Interventions to improve sexual health among the homeless community: a realist review protocol

Hau Nguyen; John Gilmore; Rikke Siersbaek; Chris Noone

doi:10.12688/hrbopenres.14193.2

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Study Protocol

Revised

Interventions to improve sexual health among the homeless community: a realist review protocol

[version 2; peer review: 3 approved]

Hau Nguyen ¹, John Gilmore², Rikke Siersbaek³, Chris Noone¹

PUBLISHED 05 May 2026

Author details Author details

¹ University of Galway, Galway, County Galway, Ireland
² University College Dublin, Dublin, Leinster, Ireland
³ The University of Dublin Trinity College, Dublin, Leinster, Ireland

Hau Nguyen
Roles: Conceptualization, Funding Acquisition, Investigation, Methodology, Project Administration, Writing – Original Draft Preparation, Writing – Review & Editing

John Gilmore
Roles: Conceptualization, Methodology, Supervision, Writing – Review & Editing

Rikke Siersbaek
Roles: Conceptualization, Methodology, Supervision, Writing – Original Draft Preparation, Writing – Review & Editing

Chris Noone
Roles: Conceptualization, Methodology, Supervision, Writing – Review & Editing

OPEN PEER REVIEW

REVIEWER STATUS

Abstract

Background

People experiencing homelessness face profound sexual health inequities, driven by overlapping structural vulnerabilities including housing instability, stigma, limited healthcare access, and social exclusion, as well as the complex lived realities associated with homelessness. Interventions designed to improve sexual health outcomes within this population are diverse, ranging from peer-led education to nurse-led clinical models and structural supports such as housing. However, the effectiveness of these interventions depends not only on their content but also on the contexts in which they are delivered and the circumstances of the populations they serve. A realist review seeks to understand how and why interventions work, for whom, and under what conditions by identifying context–mechanism–outcome configurations (CMOCs) that explain how outcomes are generated.

Methods

This review will follow Pawson’s six-step realist synthesis methodology. An initial programme theory has been developed through preliminary literature searches and will be refined iteratively as new evidence is gathered. Published and grey literature will be systematically searched and selected for their relevance to developing and testing CMOCs. Data extraction will focus on identifying key information which can contribute to understanding contextual factors, mechanisms, and outcomes across intervention types. The synthesis will develop, refine, and test theories that explain how sexual health interventions produce change in varied contexts. Patient and public involvement contributors will be consulted throughout the review to validate findings and support interpretation.

Conclusion

This review will generate transferable insights into how sexual health interventions for people experiencing homelessness work across different contexts. By identifying mechanisms that generate outcomes, and the conditions that shape them, the findings will support more context-sensitive and effective policy, practice, and service design. The results will be disseminated through peer-reviewed publications, practitioner-facing summaries, and community-informed outputs.

Keywords

Sexual health, Homelessness, Intervention, Realist review

Corresponding author: Hau Nguyen

Competing interests: No competing interests were disclosed.

Grant information: This research project is funded by the University of Galway. The funding institution did not involve in developing this review protocol.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Copyright: © 2026 Nguyen H et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

How to cite: Nguyen H, Gilmore J, Siersbaek R and Noone C. Interventions to improve sexual health among the homeless community: a realist review protocol [version 2; peer review: 3 approved]. HRB Open Res 2026, 8:83 (https://doi.org/10.12688/hrbopenres.14193.2) First published: 23 Jul 2025, 8:83 (https://doi.org/10.12688/hrbopenres.14193.1) Latest published: 05 May 2026, 8:83 (https://doi.org/10.12688/hrbopenres.14193.2)

Revised Amendments from Version 1

The manuscript has been revised in response to reviewers’ comments to improve clarity, methodological transparency, and overall coherence.
Revisions to the abstract include the addition of a brief explanation of realist review methodology and context–mechanism–outcome configurations (CMOCs), as well as clarification of the complexity of lived experiences of homelessness.
The introduction has been refined to clarify the international scope of the review while maintaining its relevance to the Irish context. Definitions of key realist concepts, including programme theory, context, and CMOCs, have been added to improve accessibility for readers unfamiliar with realist methodology.
Substantial revisions were made to the methods section. These include expanded detail on the synthesis process, outlining how data will be iteratively analysed and tested against the initial programme theory (IPT) through the development and refinement of CMOCs. Clarification has also been provided on the assessment of relevance, richness, and rigour, in line with realist review principles. Additional detail has been included on the inclusion of diverse evidence sources, including grey literature, and on supplementary search strategies such as reference list screening.
The role of the advisory group, including individuals with lived experience, has been further elaborated to clarify both the rationale for their involvement and how their participation will be supported and reported.
The initial programme theory figure, previously included in the supplementary materials, has now been incorporated into the main manuscript to improve clarity and accessibility for readers.
Finally, the dissemination section has been expanded to describe how findings will be made accessible to people experiencing homelessness through plain-language and visual outputs. No changes were made to tables or underlying data

See the authors' detailed response to the review by Wendy Masterton
See the authors' detailed response to the review by Martha Paisi

Introduction

Homelessness is a complex and dynamic condition that manifests in multiple forms. It is frequently classified into unsheltered homelessness (e.g., sleeping rough or in vehicles), sheltered homelessness (e.g., use of emergency accommodation), and hidden homelessness (e.g., temporary stays with friends or family, often unrecorded in official statistics). The European Typology of Homelessness and Housing Exclusion (ETHOS) offers a nuanced conceptual framework detailing the full spectrum of the experience of homelessness, encompassing rooflessness, houselessness, insecure housing, and inadequate housing.¹ This typology is particularly relevant for research adopting a realist approach, as it supports an examination of how varying housing circumstances shape vulnerability and access to support. Across jurisdictions, definitions of homelessness vary based on policy, legal, and service delivery frameworks. In the U.S., homelessness is narrowly defined by the Department of Housing and Urban Development (HUD) based on the absence of a fixed, adequate nighttime residence.² In contrast, Canada and Ireland adopt broader definitions. Ireland’s Housing Act of 1988, for instance, includes those whose accommodation is unsuitable or poses a risk to health and safety.³ These definitional differences reflect deeper structural and cultural assumptions about the causes and consequences of homelessness and inform how states respond.

As of early 2025, homelessness in Ireland has reached unprecedented levels, with 14,864 people recorded in emergency accommodation—the highest since national records began.⁴ Similar trends are observed internationally. For example, 771,480 people were estimated to be experiencing homelessness in the United States during the 2024 national point-in-time count, the highest figure recorded to date,⁵ while at least 382,618 people are estimated to be homeless in England at end of year 2025, including more than 175,000 children.⁶ Homelessness is underpinned by poverty, housing precarity, and systemic exclusion, and is associated with considerable disparities in physical and mental health.⁷^,⁸ Sexual health is a particularly neglected domain. The World Health Organization (WHO) defines sexual health as a state of physical, emotional, mental, and social well-being in relation to sexuality. It is not merely the absence of disease or dysfunction but requires a positive and respectful approach to sexuality and sexual relationships, as well as the possibility of having pleasurable and safe sexual experiences, free from coercion, discrimination, and violence.⁹

Sexual health encompasses a wide range of issues, including access to contraception, prevention, and treatment of sexually transmitted infections (STIs), sexual education, and the ability to engage in consensual, safe sexual activities. For the people experiencing homelessness, maintaining sexual health is particularly challenging due to the instability and risks associated with their living situations. Research indicates that people experiencing homelessness are more likely than their housed counterparts to engage in high-risk sexual behaviours, such as having unprotected sex, engaging in transactional sex, or having multiple sexual partners.¹⁰^,¹¹ These behaviours, combined with limited access to sexual health services, stigma, and the transient nature of homelessness contribute to elevated rates of STIs and other sexual health issues within this community.¹²^,¹³

Existing reviews of sexual health interventions targeting people experiencing homelessness and other high-risk populations highlight promising strategies but suffer from several shared limitations in scope and methodology. Wright and Walker conducted a narrative systematic review of sexual health interventions among homeless people who use drugs.¹⁴ While they identified potentially effective behavioural and attitude change interventions, their findings were constrained by a limited six included studies, and a lack of exploration into how circumstantial and structural factors influenced outcomes and is now outdated. A systematic review by Naranbhai et al. focused specifically on HIV prevention among young people experiencing homelessness.¹⁵ The authors were only able to include three RCTs for their review. They concluded that the lack of quality evidence and the heterogeneity in intervention characteristics hindered the synthesis of evidence regarding the effectiveness of these interventions. Brown et al. (2021) reviewed behavioural and psychosocial interventions for youth in high-risk communities.¹⁶ Like Naranbhai et al.’s review, the authors only included three studies in their review with regards to the homeless community without being able to come to conclusions as to how these interventions might work or whether they are effective as the studies were too heterogeneous to synthesise.

Notably, the aforementioned reviews were mostly restricted to trials, either intentionally or unintentionally as most non-trial studies did not meet the quality criteria to be included, which limit their ability to account for the complexity of homelessness and healthcare interventions as well as their broader circumstances. Prioritising trials also risks leaving out broader implementation studies or qualitative evaluations that could provide richer insight into how interventions function in the real world. Together, these reviews suggest that while there is emerging evidence of what works, the reliance on trials—though methodologically rigorous—often excludes valuable insights from mixed-methods, qualitative, or naturalistic studies. Such exclusions are particularly problematic in the homelessness field, where lack of funding, instability, and ethical concerns make controlled trials challenging. This highlights a pressing need for a different method for evidence synthesis that includes broader evidence base and which is specifically designed to understand complex interventions and circumstances.

Rationale

Homelessness is a significant public health issue in high-income countries.¹⁷ Communities experiencing homelessness face profound disparities in physical, mental, and sexual health due to structural and circumstantial factors, including housing instability, economic insecurity, and limited access to healthcare services. Sexual health is an often overlooked but critical aspect of wellbeing for people experiencing homelessness. Research highlights elevated rates of sexually transmitted infections (STIs), unintended pregnancies, and survival sex among this community.¹⁷ However, key questions remain unanswered: In what ways, for whom, and under what conditions do sexual health interventions work—or fail—by triggering certain mechanisms within particular settings and life situations?

A realist review is uniquely suited to address these questions. By examining a broader range of evidence, including but not limited to trials. This approach focuses on developing, refining, and testing programme theories that explain how latent powers (mechanisms) are triggered in a given context to produce outcomes.¹⁸ Rather than asking simply whether an intervention works, this review will explore how and why it works (or fails), for whom, and in what circumstances.

The current review

This realist review aims to fill the gaps identified above by systematically synthesising the published evidence to explain how sexual health interventions for homeless populations work, for whom, and under what conditions. The review will identify causal patterns of change across intervention types (e.g., peer-led, nurse-led, educational, structural) and settings, and highlight how contextual factors (e.g., housing status, service delivery models) shape outcomes. Through the development of context–mechanism–outcome configurations (CMOCs) and theories, this realist review will provide policymakers, practitioners, and service planners with a deeper understanding of how to design and deliver more responsive, equitable, and sustainable sexual health interventions for people experiencing homelessness.

Protocol

This realist review seeks to explore how and why sexual health interventions for people experiencing homelessness lead to different outcomes, depending on individual circumstances and broader social circumstances. This protocol is registered on PROSPERO (CRD420251047807).

Methods

The current review will be conducted and reported in line with the RAMESES realist review standards.¹⁹ It will follow a structured, theory-driven process composed of six iterative steps according to Pawson’s (2006) guidelines.¹⁸ These include: (i) identifying the review question, (ii) searching for primary studies, (iii) quality appraisal, (iv) extracting the data, (v) synthesizing the data and (vi) disseminating the findings.

Firstly, the scope of the review is clarified by defining the research question in realist terms—focusing on what works, for whom, in what circumstances, and how—and by developing an initial programme theory to guide inquiry. A programme theory refers to an explanation of how and why an intervention is expected to generate particular outcomes. Central to this approach is the development of CMOCs.¹⁸ These configurations describe how outcomes are produced when specific mechanisms—underlying processes or responses triggered by an intervention—are activated in particular contexts. Context refers to the social, institutional, cultural, or environmental conditions that influence whether and how these mechanisms are triggered. For example, in contexts where people experiencing homelessness have previously experienced stigma, judgement, or discrimination when accessing mainstream healthcare services (context), sexual health programmes delivered by peers or trusted outreach workers may trigger feelings of trust, recognition, and psychological safety (mechanism), leading to greater openness in discussing sexual health concerns and increased engagement with sexual health services (outcome). Secondly, a systematic search for evidence is conducted across diverse sources, including both academic and grey literature, to identify data relevant to understanding how interventions function. Thirdly, the evidence is appraised and extracted based on the relevance to the research question and the rigour of the study which produced it. Fourthly, evidence is synthesised through the development and refinement of CMOCs, and then ultimately producing theories that explain how mechanisms are triggered under different contextual conditions to produce outcomes. Iterative data searching can take place at any point during the steps 2–4. Fifthly, the programme theory is continually refined and tested throughout the review process as needed. Finally, the findings are disseminated in ways that are useful to policymakers, practitioners, and other stakeholders, emphasising transferable insights about how interventions operate.

Quality assessment

In line with realist review methodology, included sources will be appraised according to relevance, richness, and rigour.²⁰ Relevance refers to whether a source contains data that can contribute to the development, refinement, or testing of programme theory. Richness refers to the extent to which a source provides detailed conceptual or contextual information that supports explanation of how interventions work. Rigour refers to the trustworthiness of the data used to support programme theory and the coherence of the explanatory theory developed, rather than the methodological hierarchy of the study design. At the data level, rigour refers to whether the methods used to generate a particular piece of data are credible and trustworthy. This may include consideration of the study design, data collection procedures, analytical approach, and potential sources of bias. Importantly, in realist reviews rigour is applied to the specific data used to inform programme theory rather than the overall quality of the study. At the theory level, rigour will be assessed by examining the coherence and explanatory power of CMOCs. This involves assessing whether the proposed explanations are supported by evidence across multiple sources, whether they account for observed patterns in the data, and whether they are consistent with existing theoretical understandings. Where individual pieces of evidence are limited or uncertain, findings will be triangulated across multiple studies to strengthen the explanatory coherence of the programme theory. Evidence judged to be less trustworthy may still contribute to theory development but will be interpreted cautiously and supported by additional sources where possible.²⁰

Initial programme theory

Through a preliminary informal review of the literature, the authors identified a range of sexual health interventions targeting people experiencing homelessness, most of which can be categorised as one of the following categories: nurse-led, peer-led, educational or structural interventions. These interventions, varied in their design, delivery agents, and assumptions about how change occurs. Further synthesis revealed that these approaches often share underlying mechanisms and interact in complementary ways. Consequently, the authors developed an initial programme theory that captures the common mechanisms, contextual influences, and outcome pathways across these diverse interventions. This initial theory was subsequently refined through consultation with an expert advisory group, composed of professionals with experience in sexual health, homelessness, and social inclusion. Feedback gathered during a facilitated advisory panel meeting helped ensure the theory’s relevance, coherence, and grounding in real-world practice and research. Details of the initial programme theory can be seen in Figure 1.

Figure 1. Initial programme theory.

Searches

Following the principles outlined by Pawson’s (2006) guideline, the literature search for this realist review has been conducted in two phases. An initial, exploratory search was undertaken to identify key intervention types, contextual influences, and candidate mechanisms relevant to promoting sexual health among people experiencing homelessness. Along with the team’s subject area knowledge, this pilot search informed the development of an initial programme theory, which will guide the selection of search terms. A second systematic search will be undertaken with the assistance of a subject librarian. The search strategy used at the initial programme theory development stage can be found at the Open Science Framework (OSF): Interventions to improve sexual health among the homeless community: a realist review protocol. https://doi.org/10.17605/OSF.IO/W9VXY.²¹ In addition, the reference lists of the studies included will be examined to identify additional relevant sources that may not have been captured in the database searches.

Inclusion and exclusion criteria

The current review will draw on a wide range of evidence sources to develop and refine programme theories. These includes qualitative studies, quantitative research, mixed-methods studies, programme evaluations, policy documents, and grey literature such as organisational reports which provide data relevant to understanding how sexual health interventions work for people experiencing homelessness. Evidence will therefore be included based on its potential contribution to theory development and testing rather than solely on study design or methodological hierarchy.

Eligible studies must contain information that can contribute to the development or refinement of CMOCs, regardless of whether they report on intervention effectiveness. The main databases to be searched are CINAHL - Cumulative Index to Nursing and Allied Health Literature, Embase.com, MEDLINE and PsycINFO. Grey literature, policy documents, and theoretical papers will also be included where they offer explanatory insight. Studies that are not published in English will not be included. PICO criteria are as followed:

Population:

Included people experiencing homelessness or unstable housing, including subgroups (e.g., youth, LGBTQ+, those with mental health needs or substance use).

Intervention(s) or exposure(s):

Included sexual health interventions of any type (e.g., peer-led, nurse-led, educational, structural), including those integrated into wider health or social services.

Comparator(s) or control(s):

This review does not have any comparators.

Study design

Both randomized and nonrandomized study types will be included.

Data extraction and synthesis

Covidence will be used to screen retrieved articles. Data will be coded and organised using qualitative data management software NVivo. Titles and abstracts will be double screened to ensure consistency. Discrepancies will be discussed, and if consensus cannot be reached, a third reviewer will be consulted to make the final decision. The same process will be applied during full-text screening.

Expert advisory group. This review includes structured involvement from an expert advisory group, in line with best practice principles for ethical and meaningful engagement as outlined by the Irish Health Research Forum.²² This review adopts a consultation-based approach whereby experts’ consultation will be sought twice- at the initial programme theory development stage and the study completion stage. The group is composed of individuals with expertise in frontline service provision, sexual health, social inclusion, and homelessness policy. The panel includes representatives from the Health Service Executive (HSE), Safetynet Primary Care, and the Dublin Simon Community—all of whom are directly involved in delivering or coordinating services for people experiencing homelessness. It also includes academics from Trinity College Dublin, University of Galway, and University College Dublin, whose research engages directly or indirectly with issues related to homelessness, health equity, and vulnerable populations. Together, the group brings a well-rounded and practice-informed perspective to the development and refinement of the review’s programme theory. In the first phase, the group met to discuss and shape the development of the initial programme theory. This session was facilitated to gather expert insights and test the early conceptual thinking behind how sexual health services may or may not work for people experiencing homelessness. The discussions helped identify key contextual factors, mechanisms, and outcomes to guide the subsequent literature review. A second consultation will take place once the realist synthesis is complete. At that stage, the group will be invited to provide feedback on the refined, overarching programme theory, offering critical reflections on its coherence, resonance with real-world practice, and potential relevance to policy and service design. We aim to include expertise through lived experience at this stage. We recognise that individuals with lived experience of homelessness can provide important insights into how sexual health interventions are experienced in practice and whether emerging programme theories reflect real-world contexts. Their perspectives will help ensure that the review remains grounded in the realities of service access, stigma, and structural barriers that may not be fully captured in the academic literature. To support their meaningful participation, discussions will use accessible language and practical examples to explain realist concepts such as programme theory and CMOCs.

Dissemination

Results will be shared via peer-reviewed journal publications and conference presentations in the fields of public health, homelessness, and sexual health. In alignment with our commitment to patient and public involvement, accessible summaries will also be co-developed with public and patient involvement (PPI) contributors to share findings in plain language through community organisations, outreach networks, and advocacy groups. These materials will be designed to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves, using clear language and accessible formats. Key insights, particularly refined CMOCs, will be presented in visual formats such as logic models or evidence maps to support policy and practice uptake without the use of research jargon. Additionally, findings will be shared with stakeholders in health and homelessness services to inform future intervention design, delivery, and commissioning.

Conclusion

This realist review protocol outlines a comprehensive plan to investigate how sexual health interventions function for people experiencing homelessness, for whom, and under what circumstances. Moving beyond traditional systematic reviews which are designed to synthesise trial-based outcomes and effect sizes, this approach will synthesise evidence from a diverse range of study designs. By developing and testing CMOCs, the review aims to build theories that are transferable across settings. This theory-driven synthesis will help uncover the underlying mechanisms that shape intervention success or failure, while accounting for key contextual factors such as housing status and access to care. Meaningful patient and public involvement (PPI) will guide the review to ensure its relevance and impact. Ultimately, this work will inform more equitable, effective, and sustainable approaches to sexual health for the homeless community.

Review stage

The review has completed the IPT development stage, where the IPT was brought in for discussion with the expert advisory group to gather their insights and feedback. The next phase of the review will involve an in-depth literature review and realist data synthesis, aimed at testing and further refining the programme theories.

Ethical considerations

There are no ethical considerations necessary as this is a review study synthesising published literature. No primary data will be collected.

Data availability statement

Underlying data

No data associated with this article.

Extended data

Open Science Framework (OSF): Interventions to improve sexual health among the homeless community: a realist review protocol, https://doi.org/10.17605/OSF.IO/W9VXY.²¹

This project contains the following underlying data: PRISMA-P checklist, Search strategies, Initial programme theory.

Data are available under CC-By Attribution 4.0 International license.

References

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2. Department of Housing and Urban Development: Homeless Emergency Assistance and Rapid Transition to Housing (HEARTH): Defining homeless final rule.2011 [cited 2025 Jul 6]. https://www.govinfo.gov/content/pkg/FR-2011-12-05/pdf/2011-30942.pdf
3. Government of Ireland: Housing Act 1988. Irish Statute Book ; 1988.
4. Department of Housing, Local Government and Heritage: Homeless quarterly progress report for Q4 2024.Government of Ireland; 2024 [cited 2025 Jul 6]. https://www.gov.ie/en/publication/8f399-homeless-quarterly-progress-report-for-q4-2024/
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6. Shelter, the National Campaign for Homeless People Limited: At least 382,000 people are homeless in England today. 2025 [cited 2026 Mar 6]. https://england.shelter.org.uk/media/press_release/at_least_382000_people_are_homeless_in_england_today_?utm_source=chatgpt.com
7. Liu CY, Chai SJ, Watt JP: Communicable disease among people experiencing homelessness in California. Epidemiol Infect. 2020; 148: e85. PubMed Abstract | Publisher Full Text | Free Full Text
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Version 2

VERSION 2 PUBLISHED 23 Jul 2025

Author details Author details

¹ University of Galway, Galway, County Galway, Ireland
² University College Dublin, Dublin, Leinster, Ireland
³ The University of Dublin Trinity College, Dublin, Leinster, Ireland

Hau Nguyen
Roles: Conceptualization, Funding Acquisition, Investigation, Methodology, Project Administration, Writing – Original Draft Preparation, Writing – Review & Editing

John Gilmore
Roles: Conceptualization, Methodology, Supervision, Writing – Review & Editing

Rikke Siersbaek
Roles: Conceptualization, Methodology, Supervision, Writing – Original Draft Preparation, Writing – Review & Editing

Chris Noone
Roles: Conceptualization, Methodology, Supervision, Writing – Review & Editing

Competing interests

No competing interests were disclosed.

Grant information

This research project is funded by the University of Galway. The funding institution did not involve in developing this review protocol.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Article Versions (2)

version 2

Revised

Published: 05 May 2026, 8:83

https://doi.org/10.12688/hrbopenres.14193.2

version 1

Published: 23 Jul 2025, 8:83

https://doi.org/10.12688/hrbopenres.14193.1

© 2026 Nguyen H et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Nguyen H, Gilmore J, Siersbaek R and Noone C. Interventions to improve sexual health among the homeless community: a realist review protocol [version 2; peer review: 3 approved]. HRB Open Res 2026, 8:83 (https://doi.org/10.12688/hrbopenres.14193.2)

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Key to Reviewer Statuses VIEW HIDE

ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested

Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.

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Reviewer Report 23 May 2026

Jessica Sherman, The Ohio State University, Columbus, Ohio, USA

Approved

https://doi.org/10.21956/hrbopenres.15906.r55199

Thank you for the opportunity to review this protocol. I have reviewed the manuscript alongside the prior review and the authors’ responses. The protocol is clear, concise, and well written. The authors provide both a thorough description of the methods and a strong justification for their approach. They have also responded thoughtfully to prior reviewer comments, and the manuscript is strengthened as a result.

The Introduction is clear and well developed. The authors effectively convey the complexity of homelessness, including variations in definitions across countries, and provide a succinct and appropriate synthesis of the existing literature.

The Methods are well described, with sufficient detail to ensure clarity for readers who may be unfamiliar with realist methods. The authors also provide a strong rationale for using this approach to examine the sexual health of people experiencing homelessness.

Overall, this is a well-written manuscript that applies a realist approach to an important topic. It has strong potential to advance understanding of what works (and what does not) in efforts to support the sexual health of people experiencing homelessness.

Is the rationale for, and objectives of, the study clearly described?

Yes
Is the study design appropriate for the research question?

Yes
Are sufficient details of the methods provided to allow replication by others?

Yes
Are the datasets clearly presented in a useable and accessible format?

Not applicable

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: homelessness, sexual health, HIV, LGBGT+ health, mental health, substance use

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

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Reviewer Report 20 May 2026

Martha Paisi, University of Plymouth, Plymouth, UK

Approved

https://doi.org/10.21956/hrbopenres.15906.r55116

Thank you for your email and patience.

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Reviewer Report 09 May 2026

Wendy Masterton, University of Stirling, Stirling, UK

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https://doi.org/10.21956/hrbopenres.15906.r55115

I think the authors have done a good job of addressing my comments and have edited the article accordingly. The additions in methods are particularly helpful for clarity relating to the methodological approach and the CMOCs/realist terminology. The additional considerations ... Continue reading

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Reviewer Report 26 Feb 2026

Wendy Masterton, University of Stirling, Stirling, UK

Approved with Reservations

https://doi.org/10.21956/hrbopenres.15609.r53416

Thank you for the opportunity to review this protocol. It is an important topic, the protocol is considered and well written, and I am convinced by the realist approach. I have a few comments/suggestions that may strengthen it moving forward.

Introduction
I am glad to see the complexity of the homelessness definition discussed as this is important.

I did find myself wondering what the geographical focus of the review was. The authors helpfully discuss the comparisons around homelessness definitions internationally, but the focus on Ireland becomes more apparent from paragraph 2. If the review is specific to Ireland and informing Irish policy/practice, I think this needs to be made explicit in the abstract, if not the title, as well as the aim of the current review. If it is designed to be internationally relevant, I think there needs to be a little bit of editing in the Introduction section to ensure it doesn’t read as Ireland-focused.

Otherwise, the general evidence gap around the topic was clear to me, so with the above clarity, the rationale is strong.

The authors shows good knowledge of realist methodology, but the introduction would benefit from some definition work around realist terms. The term ‘programme theory’ is only loosely defined, and it isn’t clear (with a realist lens) what context means. The authors may also want to add a little about context-mechanism-outcome configurations (CMOcs) as this is more implied than explicit. Realist terminology is notoriously jargony, and clarity is essential.

Methods
The review will be clearly mapped against Pawson’s guidelines which is good. It would further strengthen the methods to state that the review will be conducted and reported in line with the RAMESES realist review standards too as I would expect these to be followed/mentioned: [Ref 1]

Helpful information provided about the IPT – this is so often missed/glossed over, so I applaud the authors for clearly explaining the IPT process and the importance of this.

Extensive search strings which is also good to see, particularly given the complexity of the topic and many different potential terms used.

It might be helpful to really emphasise that any and all types of studies/resources can be used in a realist review, this is one of the key differences from systematic reviews and is important if there is evidence in unpublished work (which I imagine there will be given the topic and organisational reports etc).

I do always question why authors decide to not include studies that are not in English without any rationale provided. There are pretty accurate free translation online now that translates articles almost immediately and to a high quality. I don’t see what the rationale is for excluding these? The exclusion may be linked to relevance to Irish context? If so, make this relevance-related consideration clearer.

There could be more clarity around synthesis. How will data be synthesised and tested against the IPTs? Will it be via NVivo or by hand?

Inclusion of the advisory group is good, and the detail around how and when they contributed is clear. However, in the paper itself, the authors will need to provide more detail around the lived experience inclusion. Realist work can be quite difficult to gain consultation on, particularly with groups who haven’t worked in a research field before, so consideration of this, and how it will be reported, will be essential. This will also be relevant when thinking about dissemination and how this could look for non-academic audiences. This is briefly mentioned in the protocol, so I would urge the authors to give ample time to this.

Is the rationale for, and objectives of, the study clearly described?

Yes
Is the study design appropriate for the research question?

Yes
Are sufficient details of the methods provided to allow replication by others?

Partly
Are the datasets clearly presented in a useable and accessible format?

Not applicable

References

1. Wong G, Greenhalgh T, Westhorp G, Buckingham J, et al.: RAMESES publication standards: realist syntheses. BMC Medicine. 2013; 11 (1). Publisher Full Text

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: substance use; harm reduction; mental health; realist methodology

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

CITE

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Author Response 05 May 2026

Hau Nguyen, University of Galway, Galway, Ireland

05 May 2026

Author Response

Masterton’s Comment Address

1.Introduction
I am glad to see the complexity of the homelessness definition discussed as this is important.
I did find myself wondering what the geographical focus ... Continue reading Masterton’s Comment Address

1.Introduction
I am glad to see the complexity of the homelessness definition discussed as this is important.
I did find myself wondering what the geographical focus of the review was. The authors helpfully discuss the comparisons around homelessness definitions internationally, but the focus on Ireland becomes more apparent from paragraph 2. If the review is specific to Ireland and informing Irish policy/practice, I think this needs to be made explicit in the abstract, if not the title, as well as the aim of the current review. If it is designed to be internationally relevant, I think there needs to be a little bit of editing in the Introduction section to ensure it doesn’t read as Ireland-focused.
Otherwise, the general evidence gap around the topic was clear to me, so with the above clarity, the rationale is strong.The authors shows good knowledge of realist methodology, but the introduction would benefit from some definition work around realist terms. The term ‘programme theory’ is only loosely defined, and it isn’t clear (with a realist lens) what context means. The authors may also want to add a little about context-mechanism-outcome configurations (CMOcs) as this is more implied than explicit. Realist terminology is notoriously jargony, and clarity is essential.
Answer:
Thank you for this helpful observation. The review aims to synthesise international evidence on sexual health interventions for people experiencing homelessness in order to develop programme theories that may be transferable across contexts. While the growing homelessness crisis in Ireland partly motivates the study, the review itself is not restricted to Irish evidence. We have revised the introduction by adding statistics from several other countries ensure the text does not appear overly Ireland-focused.
Regarding the comment regarding the programme theory, we believe that it is in regard of the method section because that is where the term was first introduced. The method section hence has been revised to provide clearer definitions of key realist concepts, including programme theory, context, and context–mechanism–outcome configurations (CMOCs), to improve accessibility for readers unfamiliar with realist methodology.

2. Methods
The review will be clearly mapped against Pawson’s guidelines which is good. It would further strengthen the methods to state that the review will be conducted and reported in line with the RAMESES realist review standards too as I would expect these to be followed/mentioned: [Ref 1]
Helpful information provided about the IPT – this is so often missed/glossed over, so I applaud the authors for clearly explaining the IPT process and the importance of this.
Extensive search strings which is also good to see, particularly given the complexity of the topic and many different potential terms used.
It might be helpful to really emphasise that any and all types of studies/resources can be used in a realist review, this is one of the key differences from systematic reviews and is important if there is evidence in unpublished work (which I imagine there will be given the topic and organisational reports etc).
I do always question why authors decide to not include studies that are not in English without any rationale provided. There are pretty accurate free translation online now that translates articles almost immediately and to a high quality. I don’t see what the rationale is for excluding these? The exclusion may be linked to relevance to Irish context? If so, make this relevance-related consideration clearer.
Answer:
Thank you for your helpful suggestions. We have reported that the review will be conducted and reported in line with the RAMESES realist review standards. We have reflected that any and all types of studies/resources can be used in a realist review in the method section. We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.
While we acknowledge that machine translation tools have improved considerably, the interpretation of qualitative and contextual information remains particularly important in realist reviews, where nuanced descriptions of mechanisms, context, and programme implementation are central to theory development. Automated translation may not reliably capture these subtleties, which could affect the interpretation of context–mechanism–outcome relationships. In addition, the review team does not have the resources to conduct formal verification of machine-translated texts. For these reasons, the review will be limited to studies published in English.

3. Data extraction and synthesis
There could be more clarity around synthesis. How will data be synthesised and tested against the IPTs? Will it be via NVivo or by hand?
Answer:
Thank you for this important comment. We have expanded the Methods section to provide greater clarity on how data will be synthesised and tested against the initial programme theory (IPT). Data synthesis will follow realist principles, involving iterative comparison of extracted data with the IPT to refine, confirm, or refute emerging context–mechanism–outcome configurations (CMOCs). This process will involve identifying patterns across studies, developing and testing explanatory propositions, and refining programme theories accordingly. We have also clarified that qualitative data management software (e.g., NVivo) may be used to support coding and organisation of data, although the analytic process will remain theory-driven and iterative rather than dependent on a specific software tool.

4.Expert Advisory Panel and Dissemination
Inclusion of the advisory group is good, and the detail around how and when they contributed is clear. However, in the paper itself, the authors will need to provide more detail around the lived experience inclusion. Realist work can be quite difficult to gain consultation on, particularly with groups who haven’t worked in a research field before, so consideration of this, and how it will be reported, will be essential. This will also be relevant when thinking about dissemination and how this could look for non-academic audiences. This is briefly mentioned in the protocol, so I would urge the authors to give ample time to this.
Answer: Thank you for this important observation. We recognise that realist methodology can be conceptually complex and that meaningful engagement with individuals who may not have prior research experience requires careful consideration. The protocol has been revised to provide further clarification on how individuals with lived experience of homelessness will be supported to engage with the review process. Lastly, the dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.
Masterton’s Comment Address

1.Introduction
I am glad to see the complexity of the homelessness definition discussed as this is important.
I did find myself wondering what the geographical focus of the review was. The authors helpfully discuss the comparisons around homelessness definitions internationally, but the focus on Ireland becomes more apparent from paragraph 2. If the review is specific to Ireland and informing Irish policy/practice, I think this needs to be made explicit in the abstract, if not the title, as well as the aim of the current review. If it is designed to be internationally relevant, I think there needs to be a little bit of editing in the Introduction section to ensure it doesn’t read as Ireland-focused.
Otherwise, the general evidence gap around the topic was clear to me, so with the above clarity, the rationale is strong.The authors shows good knowledge of realist methodology, but the introduction would benefit from some definition work around realist terms. The term ‘programme theory’ is only loosely defined, and it isn’t clear (with a realist lens) what context means. The authors may also want to add a little about context-mechanism-outcome configurations (CMOcs) as this is more implied than explicit. Realist terminology is notoriously jargony, and clarity is essential.
Answer:
Thank you for this helpful observation. The review aims to synthesise international evidence on sexual health interventions for people experiencing homelessness in order to develop programme theories that may be transferable across contexts. While the growing homelessness crisis in Ireland partly motivates the study, the review itself is not restricted to Irish evidence. We have revised the introduction by adding statistics from several other countries ensure the text does not appear overly Ireland-focused.
Regarding the comment regarding the programme theory, we believe that it is in regard of the method section because that is where the term was first introduced. The method section hence has been revised to provide clearer definitions of key realist concepts, including programme theory, context, and context–mechanism–outcome configurations (CMOCs), to improve accessibility for readers unfamiliar with realist methodology.

2. Methods
The review will be clearly mapped against Pawson’s guidelines which is good. It would further strengthen the methods to state that the review will be conducted and reported in line with the RAMESES realist review standards too as I would expect these to be followed/mentioned: [Ref 1]
Helpful information provided about the IPT – this is so often missed/glossed over, so I applaud the authors for clearly explaining the IPT process and the importance of this.
Extensive search strings which is also good to see, particularly given the complexity of the topic and many different potential terms used.
It might be helpful to really emphasise that any and all types of studies/resources can be used in a realist review, this is one of the key differences from systematic reviews and is important if there is evidence in unpublished work (which I imagine there will be given the topic and organisational reports etc).
I do always question why authors decide to not include studies that are not in English without any rationale provided. There are pretty accurate free translation online now that translates articles almost immediately and to a high quality. I don’t see what the rationale is for excluding these? The exclusion may be linked to relevance to Irish context? If so, make this relevance-related consideration clearer.
Answer:
Thank you for your helpful suggestions. We have reported that the review will be conducted and reported in line with the RAMESES realist review standards. We have reflected that any and all types of studies/resources can be used in a realist review in the method section. We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.
While we acknowledge that machine translation tools have improved considerably, the interpretation of qualitative and contextual information remains particularly important in realist reviews, where nuanced descriptions of mechanisms, context, and programme implementation are central to theory development. Automated translation may not reliably capture these subtleties, which could affect the interpretation of context–mechanism–outcome relationships. In addition, the review team does not have the resources to conduct formal verification of machine-translated texts. For these reasons, the review will be limited to studies published in English.

3. Data extraction and synthesis
There could be more clarity around synthesis. How will data be synthesised and tested against the IPTs? Will it be via NVivo or by hand?
Answer:
Thank you for this important comment. We have expanded the Methods section to provide greater clarity on how data will be synthesised and tested against the initial programme theory (IPT). Data synthesis will follow realist principles, involving iterative comparison of extracted data with the IPT to refine, confirm, or refute emerging context–mechanism–outcome configurations (CMOCs). This process will involve identifying patterns across studies, developing and testing explanatory propositions, and refining programme theories accordingly. We have also clarified that qualitative data management software (e.g., NVivo) may be used to support coding and organisation of data, although the analytic process will remain theory-driven and iterative rather than dependent on a specific software tool.

4.Expert Advisory Panel and Dissemination
Inclusion of the advisory group is good, and the detail around how and when they contributed is clear. However, in the paper itself, the authors will need to provide more detail around the lived experience inclusion. Realist work can be quite difficult to gain consultation on, particularly with groups who haven’t worked in a research field before, so consideration of this, and how it will be reported, will be essential. This will also be relevant when thinking about dissemination and how this could look for non-academic audiences. This is briefly mentioned in the protocol, so I would urge the authors to give ample time to this.
Answer: Thank you for this important observation. We recognise that realist methodology can be conceptually complex and that meaningful engagement with individuals who may not have prior research experience requires careful consideration. The protocol has been revised to provide further clarification on how individuals with lived experience of homelessness will be supported to engage with the review process. Lastly, the dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.
Competing Interests: None Close
Report a concern
Respond or Comment

COMMENTS ON THIS REPORT

Author Response 05 May 2026

Hau Nguyen, University of Galway, Galway, Ireland

05 May 2026

Author Response

Masterton’s Comment Address

1.Introduction
I am glad to see the complexity of the homelessness definition discussed as this is important.
I did find myself wondering what the geographical focus ... Continue reading Masterton’s Comment Address

1.Introduction
I am glad to see the complexity of the homelessness definition discussed as this is important.
I did find myself wondering what the geographical focus of the review was. The authors helpfully discuss the comparisons around homelessness definitions internationally, but the focus on Ireland becomes more apparent from paragraph 2. If the review is specific to Ireland and informing Irish policy/practice, I think this needs to be made explicit in the abstract, if not the title, as well as the aim of the current review. If it is designed to be internationally relevant, I think there needs to be a little bit of editing in the Introduction section to ensure it doesn’t read as Ireland-focused.
Otherwise, the general evidence gap around the topic was clear to me, so with the above clarity, the rationale is strong.The authors shows good knowledge of realist methodology, but the introduction would benefit from some definition work around realist terms. The term ‘programme theory’ is only loosely defined, and it isn’t clear (with a realist lens) what context means. The authors may also want to add a little about context-mechanism-outcome configurations (CMOcs) as this is more implied than explicit. Realist terminology is notoriously jargony, and clarity is essential.
Answer:
Thank you for this helpful observation. The review aims to synthesise international evidence on sexual health interventions for people experiencing homelessness in order to develop programme theories that may be transferable across contexts. While the growing homelessness crisis in Ireland partly motivates the study, the review itself is not restricted to Irish evidence. We have revised the introduction by adding statistics from several other countries ensure the text does not appear overly Ireland-focused.
Regarding the comment regarding the programme theory, we believe that it is in regard of the method section because that is where the term was first introduced. The method section hence has been revised to provide clearer definitions of key realist concepts, including programme theory, context, and context–mechanism–outcome configurations (CMOCs), to improve accessibility for readers unfamiliar with realist methodology.

2. Methods
The review will be clearly mapped against Pawson’s guidelines which is good. It would further strengthen the methods to state that the review will be conducted and reported in line with the RAMESES realist review standards too as I would expect these to be followed/mentioned: [Ref 1]
Helpful information provided about the IPT – this is so often missed/glossed over, so I applaud the authors for clearly explaining the IPT process and the importance of this.
Extensive search strings which is also good to see, particularly given the complexity of the topic and many different potential terms used.
It might be helpful to really emphasise that any and all types of studies/resources can be used in a realist review, this is one of the key differences from systematic reviews and is important if there is evidence in unpublished work (which I imagine there will be given the topic and organisational reports etc).
I do always question why authors decide to not include studies that are not in English without any rationale provided. There are pretty accurate free translation online now that translates articles almost immediately and to a high quality. I don’t see what the rationale is for excluding these? The exclusion may be linked to relevance to Irish context? If so, make this relevance-related consideration clearer.
Answer:
Thank you for your helpful suggestions. We have reported that the review will be conducted and reported in line with the RAMESES realist review standards. We have reflected that any and all types of studies/resources can be used in a realist review in the method section. We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.
While we acknowledge that machine translation tools have improved considerably, the interpretation of qualitative and contextual information remains particularly important in realist reviews, where nuanced descriptions of mechanisms, context, and programme implementation are central to theory development. Automated translation may not reliably capture these subtleties, which could affect the interpretation of context–mechanism–outcome relationships. In addition, the review team does not have the resources to conduct formal verification of machine-translated texts. For these reasons, the review will be limited to studies published in English.

3. Data extraction and synthesis
There could be more clarity around synthesis. How will data be synthesised and tested against the IPTs? Will it be via NVivo or by hand?
Answer:
Thank you for this important comment. We have expanded the Methods section to provide greater clarity on how data will be synthesised and tested against the initial programme theory (IPT). Data synthesis will follow realist principles, involving iterative comparison of extracted data with the IPT to refine, confirm, or refute emerging context–mechanism–outcome configurations (CMOCs). This process will involve identifying patterns across studies, developing and testing explanatory propositions, and refining programme theories accordingly. We have also clarified that qualitative data management software (e.g., NVivo) may be used to support coding and organisation of data, although the analytic process will remain theory-driven and iterative rather than dependent on a specific software tool.

4.Expert Advisory Panel and Dissemination
Inclusion of the advisory group is good, and the detail around how and when they contributed is clear. However, in the paper itself, the authors will need to provide more detail around the lived experience inclusion. Realist work can be quite difficult to gain consultation on, particularly with groups who haven’t worked in a research field before, so consideration of this, and how it will be reported, will be essential. This will also be relevant when thinking about dissemination and how this could look for non-academic audiences. This is briefly mentioned in the protocol, so I would urge the authors to give ample time to this.
Answer: Thank you for this important observation. We recognise that realist methodology can be conceptually complex and that meaningful engagement with individuals who may not have prior research experience requires careful consideration. The protocol has been revised to provide further clarification on how individuals with lived experience of homelessness will be supported to engage with the review process. Lastly, the dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.
Masterton’s Comment Address

1.Introduction
I am glad to see the complexity of the homelessness definition discussed as this is important.
I did find myself wondering what the geographical focus of the review was. The authors helpfully discuss the comparisons around homelessness definitions internationally, but the focus on Ireland becomes more apparent from paragraph 2. If the review is specific to Ireland and informing Irish policy/practice, I think this needs to be made explicit in the abstract, if not the title, as well as the aim of the current review. If it is designed to be internationally relevant, I think there needs to be a little bit of editing in the Introduction section to ensure it doesn’t read as Ireland-focused.
Otherwise, the general evidence gap around the topic was clear to me, so with the above clarity, the rationale is strong.The authors shows good knowledge of realist methodology, but the introduction would benefit from some definition work around realist terms. The term ‘programme theory’ is only loosely defined, and it isn’t clear (with a realist lens) what context means. The authors may also want to add a little about context-mechanism-outcome configurations (CMOcs) as this is more implied than explicit. Realist terminology is notoriously jargony, and clarity is essential.
Answer:
Thank you for this helpful observation. The review aims to synthesise international evidence on sexual health interventions for people experiencing homelessness in order to develop programme theories that may be transferable across contexts. While the growing homelessness crisis in Ireland partly motivates the study, the review itself is not restricted to Irish evidence. We have revised the introduction by adding statistics from several other countries ensure the text does not appear overly Ireland-focused.
Regarding the comment regarding the programme theory, we believe that it is in regard of the method section because that is where the term was first introduced. The method section hence has been revised to provide clearer definitions of key realist concepts, including programme theory, context, and context–mechanism–outcome configurations (CMOCs), to improve accessibility for readers unfamiliar with realist methodology.

2. Methods
The review will be clearly mapped against Pawson’s guidelines which is good. It would further strengthen the methods to state that the review will be conducted and reported in line with the RAMESES realist review standards too as I would expect these to be followed/mentioned: [Ref 1]
Helpful information provided about the IPT – this is so often missed/glossed over, so I applaud the authors for clearly explaining the IPT process and the importance of this.
Extensive search strings which is also good to see, particularly given the complexity of the topic and many different potential terms used.
It might be helpful to really emphasise that any and all types of studies/resources can be used in a realist review, this is one of the key differences from systematic reviews and is important if there is evidence in unpublished work (which I imagine there will be given the topic and organisational reports etc).
I do always question why authors decide to not include studies that are not in English without any rationale provided. There are pretty accurate free translation online now that translates articles almost immediately and to a high quality. I don’t see what the rationale is for excluding these? The exclusion may be linked to relevance to Irish context? If so, make this relevance-related consideration clearer.
Answer:
Thank you for your helpful suggestions. We have reported that the review will be conducted and reported in line with the RAMESES realist review standards. We have reflected that any and all types of studies/resources can be used in a realist review in the method section. We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.
While we acknowledge that machine translation tools have improved considerably, the interpretation of qualitative and contextual information remains particularly important in realist reviews, where nuanced descriptions of mechanisms, context, and programme implementation are central to theory development. Automated translation may not reliably capture these subtleties, which could affect the interpretation of context–mechanism–outcome relationships. In addition, the review team does not have the resources to conduct formal verification of machine-translated texts. For these reasons, the review will be limited to studies published in English.

3. Data extraction and synthesis
There could be more clarity around synthesis. How will data be synthesised and tested against the IPTs? Will it be via NVivo or by hand?
Answer:
Thank you for this important comment. We have expanded the Methods section to provide greater clarity on how data will be synthesised and tested against the initial programme theory (IPT). Data synthesis will follow realist principles, involving iterative comparison of extracted data with the IPT to refine, confirm, or refute emerging context–mechanism–outcome configurations (CMOCs). This process will involve identifying patterns across studies, developing and testing explanatory propositions, and refining programme theories accordingly. We have also clarified that qualitative data management software (e.g., NVivo) may be used to support coding and organisation of data, although the analytic process will remain theory-driven and iterative rather than dependent on a specific software tool.

4.Expert Advisory Panel and Dissemination
Inclusion of the advisory group is good, and the detail around how and when they contributed is clear. However, in the paper itself, the authors will need to provide more detail around the lived experience inclusion. Realist work can be quite difficult to gain consultation on, particularly with groups who haven’t worked in a research field before, so consideration of this, and how it will be reported, will be essential. This will also be relevant when thinking about dissemination and how this could look for non-academic audiences. This is briefly mentioned in the protocol, so I would urge the authors to give ample time to this.
Answer: Thank you for this important observation. We recognise that realist methodology can be conceptually complex and that meaningful engagement with individuals who may not have prior research experience requires careful consideration. The protocol has been revised to provide further clarification on how individuals with lived experience of homelessness will be supported to engage with the review process. Lastly, the dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.
Competing Interests: None Close
Report a concern

Views

Reviewer Report 22 Aug 2025

Martha Paisi, University of Plymouth, Plymouth, UK

Approved with Reservations

https://doi.org/10.21956/hrbopenres.15609.r48576

Thank you for the opportunity to review this manuscript. This is a well-articulated and methodologically sound realist review protocol that seeks to explore how, why, and under what circumstances sexual health interventions work for people experiencing homelessness. The protocol is timely, relevant, and aligned with a growing need to understand complex health interventions in vulnerable populations.

It adheres closely to established realist methodology and shows a clear commitment to rigour, stakeholder involvement, and practical impact. The topic addresses a significant gap in the literature by moving beyond effectiveness and toward contextual understanding and theory building. I would recommend 'Accept with minor revisions'.

1.Abstract
Strengths:

The abstract succinctly captures the aims, rationale, and methodological approach.

Recommendations:

The complexity of lived experience could be introduced in the background section (it is appropriately discussed in detail later in the main text).
Consider briefly defining “CMOC” or “realist review” for broader accessibility.

2. Introduction
Strengths:

Provides strong contextual background with international framing (e.g., ETHOS typology).
The complexity of both the definition and lived experience of homelessness is well captured.
Articulates the relevance of sexual health as a neglected domain among people experiencing homelessness.
Well-referenced and connects with policy and public health literature.

Recommendations:

Slight repetition of critique regarding previous reviews may be condensed.

3. Rationale and Objectives
Strengths:

Strong justification for adopting a realist approach.
Clearly identifies the gaps in the evidence base regarding sexual health interventions.

4. Methods
Strengths:

Adheres well to established realist methodology.
Describes each stage of the synthesis clearly.
Strong emphasis on theory development, iteration, and stakeholder input.

Recommendations:

Clarify how rigour and relevance will be assessed in included studies.
Consider elaborating on whether additional software (e.g., NVivo) will be used for qualitative synthesis.
Provide a short example or visualisation of how a CMOC might be constructed.

5. Programme Theory Development
Strengths:

The use of an expert advisory group enhances credibility and grounding in practice.
Transparency is ensured via registration on OSF and PROSPERO.

Recommendations:

Consider summarising or visualising the initial programme theory within the protocol.

6. Search Strategy and Inclusion Criteria
Strengths:

Inclusive of a broad range of study types and grey literature aligned with realist principles.
Appropriate databases selected.
Clear inclusion criteria using PICO-like structure adapted for realist review.

Recommendations:

To clarify whether the reference lists of included papers will be examined.

7. Data Extraction and Synthesis
Strengths:

Plans for double screening and conflict resolution are clearly stated.
Emphasis on CMOCs reflects strong realist methodology.

Recommendations:

Further clarification on how different types of data (qualitative vs quantitative) will be integrated into CMOCs would strengthen the section.
A worked example of a CMOC could aid reader understanding.

8. Stakeholder and PPI Engagement
Strengths:

Strong and ethical engagement strategy, including frontline providers and policymakers.
Intention to include individuals with lived experience at later stages is commendable and would strongly recommend.

Recommendations:

Consider more concrete description of how PPI will shape dissemination or interpretation of findings.

9. Dissemination
Strengths:

Good dissemination plans targeting academic and practitioner audiences.
Use of visual summaries and non-academic formats is excellent.

Recommendations:

Could consider discussing how findings might be made accessible to people experiencing homelessness themselves.

Is the rationale for, and objectives of, the study clearly described?

Yes
Is the study design appropriate for the research question?

Yes
Are sufficient details of the methods provided to allow replication by others?

Yes
Are the datasets clearly presented in a useable and accessible format?

Yes

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: Health equity, access to services for people expericning homelessness

CITE

Report a concern

Author Response 05 May 2026

Hau Nguyen, University of Galway, Galway, Ireland

05 May 2026

Author Response
Paisi’s Comment Address

1.Abstract:
Strengths:
- The abstract succinctly captures the aims, rationale, and methodological approach.
Recommendations:
- The complexity of lived experience could
... Continue reading
Paisi’s Comment Address

1.Abstract:
Strengths:

The abstract succinctly captures the aims, rationale, and methodological approach.

Recommendations:

The complexity of lived experience could be introduced in the background section (it is appropriately discussed in detail later in the main text).

Consider briefly defining “CMOC” or “realist review” for broader accessibility.

Answer: Thank you for this helpful suggestion. We have revised the background section of the abstract to acknowledge the complex lived experiences of people experiencing homelessness. In addition, we have included a brief clarification of realist review terminology and context–mechanism–outcome configurations (CMOCs) to improve accessibility for readers unfamiliar with realist methodology.

2.Rationale and Objective
Strengths:

Strong justification for adopting a realist approach.

Clearly identifies the gaps in the evidence base regarding sexual health interventions

3. Methods
Strengths:

Adheres well to established realist methodology.

Describes each stage of the synthesis clearly.

Strong emphasis on theory development, iteration, and stakeholder input.

Recommendations:

Clarify how rigour and relevance will be assessed in included studies.

Consider elaborating on whether additional software (e.g., NVivo) will be used for qualitative synthesis.

Provide a short example or visualisation of how a CMOC might be constructed.

Answer: Thank you for this helpful suggestion. The methods section has been expanded to provide a clearer explanation of how rigour will be assessed.
An illustrative example of a context–mechanism–outcome configuration (CMOC) has been added to the Methods section to help readers unfamiliar with realist methodology understand how CMOCs will be constructed during synthesis.
We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.

4.Initial Programme Theory

Programme Theory Development
Strengths:

The use of an expert advisory group enhances credibility and grounding in practice.

Transparency is ensured via registration on OSF and PROSPERO.

Recommendations:

Consider summarising or visualising the initial programme theory within the protocol.

Answer: Thank you very much for your suggestions. We have now visualise the initial programme theory within the protocol

5.Search Strategy and Inclusion Criteria
Strengths:

Inclusive of a broad range of study types and grey literature aligned with realist principles.

Appropriate databases selected.

Clear inclusion criteria using PICO-like structure adapted for realist review.

Recommendations:

To clarify whether the reference lists of included papers will be examined.

Answer: Thank you for your suggestion to clarify whether we will conduct backward citation for our searches. We can confirm that we do, and the following line has now been added to the section: “In addition, the reference lists of included studies will be examined to identify additional relevant sources that may not have been captured in the database searches.”

6.Data extraction and synthesis
Strengths:

Plans for double screening and conflict resolution are clearly stated.

Emphasis on CMOCs reflects strong realist methodology.

Recommendations:

Further clarification on how different types of data (qualitative vs quantitative) will be integrated into CMOCs would strengthen the section.

A worked example of a CMOC could aid reader understanding.

Answer: Thank you for your recommendation, we did add an example in section 4 of the manuscript.

7.Dissemination
Strengths:

Good dissemination plans targeting academic and practitioner audiences.

Use of visual summaries and non-academic formats is excellent.

Recommendations:

Could consider discussing how findings might be made accessible to people experiencing homelessness themselves.

Answer: Thank you for this suggestion. The dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.
Paisi’s Comment Address

1.Abstract:
Strengths:

The abstract succinctly captures the aims, rationale, and methodological approach.

Recommendations:

The complexity of lived experience could be introduced in the background section (it is appropriately discussed in detail later in the main text).

Consider briefly defining “CMOC” or “realist review” for broader accessibility.

Answer: Thank you for this helpful suggestion. We have revised the background section of the abstract to acknowledge the complex lived experiences of people experiencing homelessness. In addition, we have included a brief clarification of realist review terminology and context–mechanism–outcome configurations (CMOCs) to improve accessibility for readers unfamiliar with realist methodology.

2.Rationale and Objective
Strengths:

Strong justification for adopting a realist approach.

Clearly identifies the gaps in the evidence base regarding sexual health interventions

3. Methods
Strengths:

Adheres well to established realist methodology.

Describes each stage of the synthesis clearly.

Strong emphasis on theory development, iteration, and stakeholder input.

Recommendations:

Clarify how rigour and relevance will be assessed in included studies.

Consider elaborating on whether additional software (e.g., NVivo) will be used for qualitative synthesis.

Provide a short example or visualisation of how a CMOC might be constructed.

Answer: Thank you for this helpful suggestion. The methods section has been expanded to provide a clearer explanation of how rigour will be assessed.
An illustrative example of a context–mechanism–outcome configuration (CMOC) has been added to the Methods section to help readers unfamiliar with realist methodology understand how CMOCs will be constructed during synthesis.
We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.

4.Initial Programme Theory

Programme Theory Development
Strengths:

The use of an expert advisory group enhances credibility and grounding in practice.

Transparency is ensured via registration on OSF and PROSPERO.

Recommendations:

Consider summarising or visualising the initial programme theory within the protocol.

Answer: Thank you very much for your suggestions. We have now visualise the initial programme theory within the protocol

5.Search Strategy and Inclusion Criteria
Strengths:

Inclusive of a broad range of study types and grey literature aligned with realist principles.

Appropriate databases selected.

Clear inclusion criteria using PICO-like structure adapted for realist review.

Recommendations:

To clarify whether the reference lists of included papers will be examined.

Answer: Thank you for your suggestion to clarify whether we will conduct backward citation for our searches. We can confirm that we do, and the following line has now been added to the section: “In addition, the reference lists of included studies will be examined to identify additional relevant sources that may not have been captured in the database searches.”

6.Data extraction and synthesis
Strengths:

Plans for double screening and conflict resolution are clearly stated.

Emphasis on CMOCs reflects strong realist methodology.

Recommendations:

Further clarification on how different types of data (qualitative vs quantitative) will be integrated into CMOCs would strengthen the section.

A worked example of a CMOC could aid reader understanding.

Answer: Thank you for your recommendation, we did add an example in section 4 of the manuscript.

7.Dissemination
Strengths:

Good dissemination plans targeting academic and practitioner audiences.

Use of visual summaries and non-academic formats is excellent.

Recommendations:

Could consider discussing how findings might be made accessible to people experiencing homelessness themselves.

Answer: Thank you for this suggestion. The dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.
Competing Interests: None Close
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Respond or Comment

COMMENTS ON THIS REPORT

Author Response 05 May 2026

Hau Nguyen, University of Galway, Galway, Ireland

05 May 2026

Author Response
Paisi’s Comment Address

1.Abstract:
Strengths:
- The abstract succinctly captures the aims, rationale, and methodological approach.
Recommendations:
- The complexity of lived experience could
... Continue reading
Paisi’s Comment Address

1.Abstract:
Strengths:

The abstract succinctly captures the aims, rationale, and methodological approach.

Recommendations:

The complexity of lived experience could be introduced in the background section (it is appropriately discussed in detail later in the main text).

Consider briefly defining “CMOC” or “realist review” for broader accessibility.

Answer: Thank you for this helpful suggestion. We have revised the background section of the abstract to acknowledge the complex lived experiences of people experiencing homelessness. In addition, we have included a brief clarification of realist review terminology and context–mechanism–outcome configurations (CMOCs) to improve accessibility for readers unfamiliar with realist methodology.

2.Rationale and Objective
Strengths:

Strong justification for adopting a realist approach.

Clearly identifies the gaps in the evidence base regarding sexual health interventions

3. Methods
Strengths:

Adheres well to established realist methodology.

Describes each stage of the synthesis clearly.

Strong emphasis on theory development, iteration, and stakeholder input.

Recommendations:

Clarify how rigour and relevance will be assessed in included studies.

Consider elaborating on whether additional software (e.g., NVivo) will be used for qualitative synthesis.

Provide a short example or visualisation of how a CMOC might be constructed.

Answer: Thank you for this helpful suggestion. The methods section has been expanded to provide a clearer explanation of how rigour will be assessed.
An illustrative example of a context–mechanism–outcome configuration (CMOC) has been added to the Methods section to help readers unfamiliar with realist methodology understand how CMOCs will be constructed during synthesis.
We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.

4.Initial Programme Theory

Programme Theory Development
Strengths:

The use of an expert advisory group enhances credibility and grounding in practice.

Transparency is ensured via registration on OSF and PROSPERO.

Recommendations:

Consider summarising or visualising the initial programme theory within the protocol.

Answer: Thank you very much for your suggestions. We have now visualise the initial programme theory within the protocol

5.Search Strategy and Inclusion Criteria
Strengths:

Inclusive of a broad range of study types and grey literature aligned with realist principles.

Appropriate databases selected.

Clear inclusion criteria using PICO-like structure adapted for realist review.

Recommendations:

To clarify whether the reference lists of included papers will be examined.

Answer: Thank you for your suggestion to clarify whether we will conduct backward citation for our searches. We can confirm that we do, and the following line has now been added to the section: “In addition, the reference lists of included studies will be examined to identify additional relevant sources that may not have been captured in the database searches.”

6.Data extraction and synthesis
Strengths:

Plans for double screening and conflict resolution are clearly stated.

Emphasis on CMOCs reflects strong realist methodology.

Recommendations:

Further clarification on how different types of data (qualitative vs quantitative) will be integrated into CMOCs would strengthen the section.

A worked example of a CMOC could aid reader understanding.

Answer: Thank you for your recommendation, we did add an example in section 4 of the manuscript.

7.Dissemination
Strengths:

Good dissemination plans targeting academic and practitioner audiences.

Use of visual summaries and non-academic formats is excellent.

Recommendations:

Could consider discussing how findings might be made accessible to people experiencing homelessness themselves.

Answer: Thank you for this suggestion. The dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.
Paisi’s Comment Address

1.Abstract:
Strengths:

The abstract succinctly captures the aims, rationale, and methodological approach.

Recommendations:

The complexity of lived experience could be introduced in the background section (it is appropriately discussed in detail later in the main text).

Consider briefly defining “CMOC” or “realist review” for broader accessibility.

Answer: Thank you for this helpful suggestion. We have revised the background section of the abstract to acknowledge the complex lived experiences of people experiencing homelessness. In addition, we have included a brief clarification of realist review terminology and context–mechanism–outcome configurations (CMOCs) to improve accessibility for readers unfamiliar with realist methodology.

2.Rationale and Objective
Strengths:

Strong justification for adopting a realist approach.

Clearly identifies the gaps in the evidence base regarding sexual health interventions

3. Methods
Strengths:

Adheres well to established realist methodology.

Describes each stage of the synthesis clearly.

Strong emphasis on theory development, iteration, and stakeholder input.

Recommendations:

Clarify how rigour and relevance will be assessed in included studies.

Consider elaborating on whether additional software (e.g., NVivo) will be used for qualitative synthesis.

Provide a short example or visualisation of how a CMOC might be constructed.

Answer: Thank you for this helpful suggestion. The methods section has been expanded to provide a clearer explanation of how rigour will be assessed.
An illustrative example of a context–mechanism–outcome configuration (CMOC) has been added to the Methods section to help readers unfamiliar with realist methodology understand how CMOCs will be constructed during synthesis.
We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.

4.Initial Programme Theory

Programme Theory Development
Strengths:

The use of an expert advisory group enhances credibility and grounding in practice.

Transparency is ensured via registration on OSF and PROSPERO.

Recommendations:

Consider summarising or visualising the initial programme theory within the protocol.

Answer: Thank you very much for your suggestions. We have now visualise the initial programme theory within the protocol

5.Search Strategy and Inclusion Criteria
Strengths:

Inclusive of a broad range of study types and grey literature aligned with realist principles.

Appropriate databases selected.

Clear inclusion criteria using PICO-like structure adapted for realist review.

Recommendations:

To clarify whether the reference lists of included papers will be examined.

Answer: Thank you for your suggestion to clarify whether we will conduct backward citation for our searches. We can confirm that we do, and the following line has now been added to the section: “In addition, the reference lists of included studies will be examined to identify additional relevant sources that may not have been captured in the database searches.”

6.Data extraction and synthesis
Strengths:

Plans for double screening and conflict resolution are clearly stated.

Emphasis on CMOCs reflects strong realist methodology.

Recommendations:

Further clarification on how different types of data (qualitative vs quantitative) will be integrated into CMOCs would strengthen the section.

A worked example of a CMOC could aid reader understanding.

Answer: Thank you for your recommendation, we did add an example in section 4 of the manuscript.

7.Dissemination
Strengths:

Good dissemination plans targeting academic and practitioner audiences.

Use of visual summaries and non-academic formats is excellent.

Recommendations:

Could consider discussing how findings might be made accessible to people experiencing homelessness themselves.

Answer: Thank you for this suggestion. The dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.
Competing Interests: None Close
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Version 2

VERSION 2 PUBLISHED 23 Jul 2025

Open Peer Review

Reviewer Status

Reviewer Reports

	Invited Reviewers
	1	2	3
Version 2 (revision) 05 May 26	read	read	read
Version 1 23 Jul 25	read	read

Martha Paisi, University of Plymouth, Plymouth, UK
Wendy Masterton, University of Stirling, Stirling, UK
Jessica Sherman, The Ohio State University, Columbus, USA

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Reviewer Report

3 Views

23 May 2026 | for Version 2

Jessica Sherman, The Ohio State University, Columbus, Ohio, USA

3 Views Cite this report Responses(0)

Approved

Is the rationale for, and objectives of, the study clearly described?

Yes
Is the study design appropriate for the research question?

Yes
Are sufficient details of the methods provided to allow replication by others?

Yes
Are the datasets clearly presented in a useable and accessible format?

Not applicable

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

homelessness, sexual health, HIV, LGBGT+ health, mental health, substance use

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

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Reviewer Report

8 Views

20 May 2026 | for Version 2

Martha Paisi, University of Plymouth, Plymouth, UK

8 Views Cite this report Responses(0)

Approved

Thank you for your email and patience.

I have revised the newer version and I believe in its current form, it is suitable for indexing.

Competing Interests

No competing interests were disclosed.

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

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Reviewer Report

9 Views

09 May 2026 | for Version 2

Wendy Masterton, University of Stirling, Stirling, UK

9 Views Cite this report Responses(0)

Approved

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

substance use; harm reduction; mental health; realist methodology

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

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Reviewer Report

27 Views

26 Feb 2026 | for Version 1

Wendy Masterton, University of Stirling, Stirling, UK

27 Views Cite this report Responses(1)

Approved With Reservations

Is the rationale for, and objectives of, the study clearly described?

Yes
Is the study design appropriate for the research question?

Yes
Are sufficient details of the methods provided to allow replication by others?

Partly
Are the datasets clearly presented in a useable and accessible format?

Not applicable

References

1. Wong G, Greenhalgh T, Westhorp G, Buckingham J, et al.: RAMESES publication standards: realist syntheses. BMC Medicine. 2013; 11 (1). Publisher Full Text

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

substance use; harm reduction; mental health; realist methodology

Respond to this report

Responses (1)

Author Response

05 May 2026

Hau Nguyen, University of Galway, Galway, Ireland

Masterton’s Comment Address

1.Introduction
I am glad to see the complexity of the homelessness definition discussed as this is important.
I did find myself wondering what the geographical focus of the review was. The authors helpfully discuss the comparisons around homelessness definitions internationally, but the focus on Ireland becomes more apparent from paragraph 2. If the review is specific to Ireland and informing Irish policy/practice, I think this needs to be made explicit in the abstract, if not the title, as well as the aim of the current review. If it is designed to be internationally relevant, I think there needs to be a little bit of editing in the Introduction section to ensure it doesn’t read as Ireland-focused.
Otherwise, the general evidence gap around the topic was clear to me, so with the above clarity, the rationale is strong.The authors shows good knowledge of realist methodology, but the introduction would benefit from some definition work around realist terms. The term ‘programme theory’ is only loosely defined, and it isn’t clear (with a realist lens) what context means. The authors may also want to add a little about context-mechanism-outcome configurations (CMOcs) as this is more implied than explicit. Realist terminology is notoriously jargony, and clarity is essential.
Answer:
Thank you for this helpful observation. The review aims to synthesise international evidence on sexual health interventions for people experiencing homelessness in order to develop programme theories that may be transferable across contexts. While the growing homelessness crisis in Ireland partly motivates the study, the review itself is not restricted to Irish evidence. We have revised the introduction by adding statistics from several other countries ensure the text does not appear overly Ireland-focused.
Regarding the comment regarding the programme theory, we believe that it is in regard of the method section because that is where the term was first introduced. The method section hence has been revised to provide clearer definitions of key realist concepts, including programme theory, context, and context–mechanism–outcome configurations (CMOCs), to improve accessibility for readers unfamiliar with realist methodology.

2. Methods
The review will be clearly mapped against Pawson’s guidelines which is good. It would further strengthen the methods to state that the review will be conducted and reported in line with the RAMESES realist review standards too as I would expect these to be followed/mentioned: [Ref 1]
Helpful information provided about the IPT – this is so often missed/glossed over, so I applaud the authors for clearly explaining the IPT process and the importance of this.
Extensive search strings which is also good to see, particularly given the complexity of the topic and many different potential terms used.
It might be helpful to really emphasise that any and all types of studies/resources can be used in a realist review, this is one of the key differences from systematic reviews and is important if there is evidence in unpublished work (which I imagine there will be given the topic and organisational reports etc).
I do always question why authors decide to not include studies that are not in English without any rationale provided. There are pretty accurate free translation online now that translates articles almost immediately and to a high quality. I don’t see what the rationale is for excluding these? The exclusion may be linked to relevance to Irish context? If so, make this relevance-related consideration clearer.
Answer:
Thank you for your helpful suggestions. We have reported that the review will be conducted and reported in line with the RAMESES realist review standards. We have reflected that any and all types of studies/resources can be used in a realist review in the method section. We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.
While we acknowledge that machine translation tools have improved considerably, the interpretation of qualitative and contextual information remains particularly important in realist reviews, where nuanced descriptions of mechanisms, context, and programme implementation are central to theory development. Automated translation may not reliably capture these subtleties, which could affect the interpretation of context–mechanism–outcome relationships. In addition, the review team does not have the resources to conduct formal verification of machine-translated texts. For these reasons, the review will be limited to studies published in English.

3. Data extraction and synthesis
There could be more clarity around synthesis. How will data be synthesised and tested against the IPTs? Will it be via NVivo or by hand?
Answer:
Thank you for this important comment. We have expanded the Methods section to provide greater clarity on how data will be synthesised and tested against the initial programme theory (IPT). Data synthesis will follow realist principles, involving iterative comparison of extracted data with the IPT to refine, confirm, or refute emerging context–mechanism–outcome configurations (CMOCs). This process will involve identifying patterns across studies, developing and testing explanatory propositions, and refining programme theories accordingly. We have also clarified that qualitative data management software (e.g., NVivo) may be used to support coding and organisation of data, although the analytic process will remain theory-driven and iterative rather than dependent on a specific software tool.

4.Expert Advisory Panel and Dissemination
Inclusion of the advisory group is good, and the detail around how and when they contributed is clear. However, in the paper itself, the authors will need to provide more detail around the lived experience inclusion. Realist work can be quite difficult to gain consultation on, particularly with groups who haven’t worked in a research field before, so consideration of this, and how it will be reported, will be essential. This will also be relevant when thinking about dissemination and how this could look for non-academic audiences. This is briefly mentioned in the protocol, so I would urge the authors to give ample time to this.
Answer: Thank you for this important observation. We recognise that realist methodology can be conceptually complex and that meaningful engagement with individuals who may not have prior research experience requires careful consideration. The protocol has been revised to provide further clarification on how individuals with lived experience of homelessness will be supported to engage with the review process. Lastly, the dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.

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Competing Interests

None

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Reviewer Report

26 Views

22 Aug 2025 | for Version 1

Martha Paisi, University of Plymouth, Plymouth, UK

26 Views Cite this report Responses(1)

Approved With Reservations

The abstract succinctly captures the aims, rationale, and methodological approach.

Recommendations:

The complexity of lived experience could be introduced in the background section (it is appropriately discussed in detail later in the main text).
Consider briefly defining “CMOC” or “realist review” for broader accessibility.

2. Introduction
Strengths:

Provides strong contextual background with international framing (e.g., ETHOS typology).
The complexity of both the definition and lived experience of homelessness is well captured.
Articulates the relevance of sexual health as a neglected domain among people experiencing homelessness.
Well-referenced and connects with policy and public health literature.

Recommendations:

Slight repetition of critique regarding previous reviews may be condensed.

3. Rationale and Objectives
Strengths:

Strong justification for adopting a realist approach.
Clearly identifies the gaps in the evidence base regarding sexual health interventions.

4. Methods
Strengths:

Adheres well to established realist methodology.
Describes each stage of the synthesis clearly.
Strong emphasis on theory development, iteration, and stakeholder input.

Recommendations:

Clarify how rigour and relevance will be assessed in included studies.
Consider elaborating on whether additional software (e.g., NVivo) will be used for qualitative synthesis.
Provide a short example or visualisation of how a CMOC might be constructed.

5. Programme Theory Development
Strengths:

The use of an expert advisory group enhances credibility and grounding in practice.
Transparency is ensured via registration on OSF and PROSPERO.

Recommendations:

Consider summarising or visualising the initial programme theory within the protocol.

6. Search Strategy and Inclusion Criteria
Strengths:

Inclusive of a broad range of study types and grey literature aligned with realist principles.
Appropriate databases selected.
Clear inclusion criteria using PICO-like structure adapted for realist review.

Recommendations:

To clarify whether the reference lists of included papers will be examined.

7. Data Extraction and Synthesis
Strengths:

Plans for double screening and conflict resolution are clearly stated.
Emphasis on CMOCs reflects strong realist methodology.

Recommendations:

Further clarification on how different types of data (qualitative vs quantitative) will be integrated into CMOCs would strengthen the section.
A worked example of a CMOC could aid reader understanding.

8. Stakeholder and PPI Engagement
Strengths:

Strong and ethical engagement strategy, including frontline providers and policymakers.
Intention to include individuals with lived experience at later stages is commendable and would strongly recommend.

Recommendations:

Consider more concrete description of how PPI will shape dissemination or interpretation of findings.

9. Dissemination
Strengths:

Good dissemination plans targeting academic and practitioner audiences.
Use of visual summaries and non-academic formats is excellent.

Recommendations:

Could consider discussing how findings might be made accessible to people experiencing homelessness themselves.

Is the rationale for, and objectives of, the study clearly described?

Yes
Is the study design appropriate for the research question?

Yes
Are sufficient details of the methods provided to allow replication by others?

Yes
Are the datasets clearly presented in a useable and accessible format?

Yes

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Health equity, access to services for people expericning homelessness

Respond to this report

Responses (1)

Author Response

05 May 2026

Hau Nguyen, University of Galway, Galway, Ireland

Paisi’s Comment Address

1.Abstract:
Strengths:

The abstract succinctly captures the aims, rationale, and methodological approach.

Recommendations:

The complexity of lived experience could be introduced in the background section (it is appropriately discussed in detail later in the main text).
Consider briefly defining “CMOC” or “realist review” for broader accessibility.

Answer: Thank you for this helpful suggestion. We have revised the background section of the abstract to acknowledge the complex lived experiences of people experiencing homelessness. In addition, we have included a brief clarification of realist review terminology and context–mechanism–outcome configurations (CMOCs) to improve accessibility for readers unfamiliar with realist methodology.

2.Rationale and Objective
Strengths:

Strong justification for adopting a realist approach.
Clearly identifies the gaps in the evidence base regarding sexual health interventions

3. Methods
Strengths:

Adheres well to established realist methodology.
Describes each stage of the synthesis clearly.
Strong emphasis on theory development, iteration, and stakeholder input.

Recommendations:

Clarify how rigour and relevance will be assessed in included studies.
Consider elaborating on whether additional software (e.g., NVivo) will be used for qualitative synthesis.
Provide a short example or visualisation of how a CMOC might be constructed.

Answer: Thank you for this helpful suggestion. The methods section has been expanded to provide a clearer explanation of how rigour will be assessed.
An illustrative example of a context–mechanism–outcome configuration (CMOC) has been added to the Methods section to help readers unfamiliar with realist methodology understand how CMOCs will be constructed during synthesis.
We have also clarified that qualitative data management software NVivo will be used to support coding and organisation of data during the synthesis process.

4.Initial Programme Theory

Programme Theory Development
Strengths:

The use of an expert advisory group enhances credibility and grounding in practice.
Transparency is ensured via registration on OSF and PROSPERO.

Recommendations:

Consider summarising or visualising the initial programme theory within the protocol.

Answer: Thank you very much for your suggestions. We have now visualise the initial programme theory within the protocol

5.Search Strategy and Inclusion Criteria
Strengths:

Inclusive of a broad range of study types and grey literature aligned with realist principles.
Appropriate databases selected.
Clear inclusion criteria using PICO-like structure adapted for realist review.

Recommendations:

To clarify whether the reference lists of included papers will be examined.

Answer: Thank you for your suggestion to clarify whether we will conduct backward citation for our searches. We can confirm that we do, and the following line has now been added to the section: “In addition, the reference lists of included studies will be examined to identify additional relevant sources that may not have been captured in the database searches.”

6.Data extraction and synthesis
Strengths:

Plans for double screening and conflict resolution are clearly stated.
Emphasis on CMOCs reflects strong realist methodology.

Recommendations:

Further clarification on how different types of data (qualitative vs quantitative) will be integrated into CMOCs would strengthen the section.
A worked example of a CMOC could aid reader understanding.

Answer: Thank you for your recommendation, we did add an example in section 4 of the manuscript.

7.Dissemination
Strengths:

Good dissemination plans targeting academic and practitioner audiences.
Use of visual summaries and non-academic formats is excellent.

Recommendations:

Could consider discussing how findings might be made accessible to people experiencing homelessness themselves.

Answer: Thank you for this suggestion. The dissemination section has been revised to clarify that outputs will be developed in accessible formats and shared through community organisations and outreach networks to ensure that findings are accessible not only to practitioners and policymakers but also to people experiencing homelessness themselves.

View more View less

Competing Interests

None

Alongside their report, reviewers assign a status to the article:

Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested

Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.

Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions

[1] 1. FEANTSA: How to measure and monitor homelessness at EU level. Brussels: FEANTSA; 2010.

[2] 2. Department of Housing and Urban Development: Homeless Emergency Assistance and Rapid Transition to Housing (HEARTH): Defining homeless final rule.2011 [cited 2025 Jul 6]. https://www.govinfo.gov/content/pkg/FR-2011-12-05/pdf/2011-30942.pdf

[3] 3. Government of Ireland: Housing Act 1988. Irish Statute Book ; 1988.

[4] 4. Department of Housing, Local Government and Heritage: Homeless quarterly progress report for Q4 2024.Government of Ireland; 2024 [cited 2025 Jul 6]. https://www.gov.ie/en/publication/8f399-homeless-quarterly-progress-report-for-q4-2024/

[5] 5. The US Department of Housing and Urban Development: The 2024 Annual Homelessness Assessment Report (AHAR) to Congress. 2024 [cited 2026 Mar 6]. https://www.huduser.gov/portal/sites/default/files/pdf/2024-AHAR-Part-1.pdf

[6] 6. Shelter, the National Campaign for Homeless People Limited: At least 382,000 people are homeless in England today. 2025 [cited 2026 Mar 6]. https://england.shelter.org.uk/media/press_release/at_least_382000_people_are_homeless_in_england_today_?utm_source=chatgpt.com

[7] 7. Liu CY, Chai SJ, Watt JP: Communicable disease among people experiencing homelessness in California. Epidemiol Infect. 2020; 148: e85. PubMed Abstract | Publisher Full Text | Free Full Text

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Interventions to improve sexual health among the homeless community: a realist review protocol

Abstract

Background

Methods

Conclusion

Keywords

Revised Amendments from Version 1

Introduction

Rationale

The current review

Protocol

Methods

Quality assessment

Initial programme theory

Figure 1. Initial programme theory.

Searches

Inclusion and exclusion criteria

Study design

Data extraction and synthesis

Dissemination

Conclusion

Review stage

Ethical considerations

Data availability statement

Underlying data

Extended data

References

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Interventions to improve sexual health among the homeless community: a realist review protocol

Abstract

Background

Methods

Conclusion

Keywords

Revised Amendments from Version 1

Introduction

Rationale

The current review

Protocol

Methods

Quality assessment

Initial programme theory

Figure 1. Initial programme theory.

Searches

Inclusion and exclusion criteria

Study design

Data extraction and synthesis

Dissemination

Conclusion

Review stage

Ethical considerations

Data availability statement

Underlying data

Extended data

References

Comments on this article Comments (0)

Open Peer Review

Comments on this article Comments (0)

Open Peer Review

Reviewer Status

Reviewer Reports

Comments on this article

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