Table 1

Study characteristics

Author (year)	Setting	Objectives	Study design	Participants	Interview method	Intervention	Results
Jackson et al (2021)87	South Africa	Test the intervention effectiveness for pain severity and interference, depressive symptoms, HRQoL and self-efficacy.	Non-randomised controlled trial	49 female PLHIV (intervention group n=26, control group n=23)	NA	Intervention group: the peer support and the therapeutic relationship; control group: therapeutic relationship alone. Peer support: 6 weekly 2-hour group sessions.	Both intervention groups were similarly effective in significantly reducing pain severity and interference, depressive symptoms, increasing self-efficacy and HRQoL over the 48 weeks.
Hart et al (2021)12	Canada	Test the intervention effectiveness for safe sexual behaviours, loneliness, sexual compulsivity and condom self-efficacy.	Randomised controlled trial	183 HIV+gay, bisexual and other men who have sex with men (intervention group n=89, control group n=94)	NA	Eight weekly 2-hour group sessions.	The intervention resulted in 43% relative reduction at 3-month follow-up in condomless anal sex with serodiscordant partners and significant reductions in sexual compulsivity, which indicated the intervention could promote the sexual health of higher risk populations.
Enriquez et al (2019)58	USA	Test the intervention effectiveness for HIV viral load suppression and engagement in HIV care.	Randomised controlled trial	30 PLHIV (intervention group n=20, control group n=10)	NA	Seven individual sessions: one session per week for 6 consecutive weeks with a booster session 6 weeks later.	65% of the participants in the intervention group had viral load suppression and 100% remained in care at 12 months postintervention. Impact on viral load was significant, suggesting that peers are effective change agents who positively impacted outcomes for individuals struggling with adherence to HIV treatment.
Knudson et al (2019)13	China	Explore the implementation of the interactive, texted, check-in messages and the kinds of issues MSM brought up with peer counsellors during follow-up discussions.	Randomised controlled trial	367 HIV-infected MSM (intervention group n=184, control group n=183)	NA	Five patient-focused, face-to-face peer-counselling (PC) sessions delivered over the first 9 months of participation, and a short message service (SMS) sent weekly for the first 6 months and every 2 weeks for the last 6 months.	A wide variety of topics were discussed with PCs. Sending regular check-ins may offer unique opportunities for newly diagnosed MSM to ask questions or gather support between face-to-face visits.
Cabral et al (2018)61	USA	Test the intervention effectiveness for retention in care and viral suppression at 12 months, HIV knowledge, self-efficacy, physical and mental health quality of life.	Randomised controlled trial	348 PLHIV (intervention group n=174, control group n=174)	NA	Seven one-on-one educational sessions for 60 min every 1–3 weeks. The peer also conducted weekly check-ins by phone or in person which ranged from 30 to 60 min or every 2 weeks for up to 4 months.	Peer interventions may improve retention in primary care among subgroups of people living with HIV from racial/ethnic minority communities, although such improved retention may not increase viral load suppression.
Liu et al (2018)14	China	Test the intervention effectiveness for ART initiation/adherence, high-risk behaviours change, quality of life, HIV stigma, self-efficacy, hospital anxiety and depression.	Randomised controlled trial	367 newly diagnosed HIV-positive men (intervention group n=184, control group n=183)	NA	The PC session involved a one-on-one 60-min discussion focusing on topics regarding specific high-risk behaviours modification.	PC was helpful to reduce inserted anal sex, condomless anal sex and illicit drug use.
Senn et al (2017)92	USA	Evaluate the feasibility of a peer support text messaging intervention designed to increase retention in HIV care and HIV medication adherence among HIV-infected black MSM.	One arm pilot study	8 HIV-infected black MSM	NA	Peer mentors were asked to respond within 12 hours when a PLHIV sent a text in a developed application, and were asked to reach out to them if they had not heard from them in 3 days.	The peer mentor text messaging intervention was feasible. Some PLHIV desired more frequent contact with peers, and peers reported that other commitments made it difficult at times to be fully engaged. Both peers and PLHIV desired more personalised contact.
Giordano et al (2016)90	USA	Test the intervention effectiveness for retention in care and viral load improvement 6 months after discharge.	Randomised controlled trial	417 PLHIV (intervention group n=202, control group n=215)	NA	The intervention included two in-person sessions with a volunteer peer mentor while hospitalised, followed by five phone calls in the 10 weeks after discharge.	There were no significant differences for all the outcomes.
Cuong (2016)	Vietnam	Test the intervention effectiveness for virological failure and CD4 trends.	Cluster randomised controlled trial	640 PLHIV (intervention group n=332, control group n=308)	NA	The intervention performed by peer-supporters were home-based visits that provided twice a week in the first 2 months, then once a week when patients’ adherence passed assessments. Additional visits were provided if patients were sick or had a serious ADR or a history of poor adherence.	Peer support did not show any impact on virological and immunological outcomes after 2 years of follow-up.
Parker et al (2016)59	South Africa	Test the intervention effectiveness for pain severity and interference, depression, HRQoL and self-efficacy.	Randomised controlled trial	27 female PLHIV (intervention group n=12, control group n=15)	NA	The intervention included a workbook in which problem solving and goal setting worksheets were presented specifically relating to different weekly topics and a 20-min aerobic and strengthening exercise circuit which was increased by 2 min each week. Each session of the intervention concluded with guided relaxation. The intervention was delivered over 2 hours in a peer-led format on a weekly basis for 6 weeks, a total of 12 hours.	Provision of a workbook and participating in a 6-week peer-led exercise and education intervention are efficacious methods to treat pain for women living with HIV/AIDS.
Chang et al (2015)62	Uganda	Test the intervention effectiveness for sexual behaviours, HIV clinic attendance and HIV preventive care intervention usage.	Randomised controlled trial	442 PLHIV (intervention group n=221, control group n=221)	NA	Peers performed three categories of activities: (1) Assessment-Peers assessed participants' clinical status, clinic attendance, BCP adherence and sexual behaviours using a structured interview form; (2) Support-Peers provided psychosocial support, encouragement, information on and reminders of clinic appointments and the BCP and counselling on reducing risky sexual behaviours; (3) Access-Peers provided triage to higher level care if necessary.	After 1 year, intervention participants were more likely to report being in care, on cotrimoxazole, and safe water vessel adherence, indicated that peer support may be an effective intervention to facilitate pre-ART care compliance.
Enriquez et al (2015)63	USA	Test the intervention effectiveness for medication adherence, viral load and readiness for healthy behaviour change.	Randomised controlled trial	20 PLHIV (intervention group n=10, control group n=10)	NA	Six individual sessions, lasting approximately 1 hour, which occurred once weekly for 6 consecutive weeks. A booster intervention session was delivered 1 month after the initial 6 weekly intervention sessions.	Treatment group had significantly improved adherence. MEMS (Medication Event Monitoring System) and pharmacy refill data correlated with viral load log drop. Higher readiness for healthy behaviour change correlated with viral load drop and approached significance.
Masquillier et al (2014)88	South Africa	Analyse the impact of peer adherence support (PAS) intervention and the family environment on the state of hope; investigate the inter-relationship between this type of intervention and the immediate social context in which a patient life.	Randomised controlled trial	498 PLHIV	NA	A group receiving additional biweekly PAS for a period of 18 months. Peer adherence supporters provided support with adherence and discussed matters that can make adherence more difficult (eg, stigma). They identified possible side effects of ART and acted appropriately.	Neither PAS nor the family environment has a direct effect on the level of hope in PLHIV. There was a positive significant interaction between family functioning and PAS, indicating that better family functioning increases the positive effect of PAS on the state of hope.
Van Tam et al (2012)60	Vietnam	Assess the effect of peer support on QOL and internal stigma during the first year after initiating ART.	Cluster randomised controlled trial	228 PLHIV (intervention group n=119, control group n=109)	NA	Biweekly visits during the initial 2 months of ART. After 2 months, the visits were reduced to once per week or intensified to become more frequent.	The peer support intervention improved QOL after 12 months among ART patients presenting at clinical stages 3 and 4 at baseline, but it had no impact on QOL among ART patients enrolled at clinical stages 1 and 2. The intervention did not have an effect on internal stigma.
Chang et al (2010)57	Uganda	Assess the effect of community-based peer health workers (PHW) on adherence and cumulative risk of virological failure, virological failure at each 24-week time point up to 192 weeks of antiretroviral therapy, mortality, lost to follow-up and CD4 change at 24 and 48 weeks of ART.	Cluster randomised controlled trial	1336 PLHIV	NA	PHW tasks included providing ART counselling and support in group and individual sessions. For their home visit tasks, PHWs were initially assigned about 15 patients each who were visited biweekly.	A PHW intervention was associated with decreased virological failure rates occurring 96 weeks and longer into ART, but did not affect cumulative risk of virological failure, adherence measures or shorter-term virological outcomes. PHWs may be an effective intervention to sustain long-term ART in low-resource settings.
Ruiz et al (2010)91	Spain	Compare the efficacy of two interventions to improve treatment adherence: one conducted by a health professional and the other by a ‘peer’.	Randomised controlled trial	198 PLHIV (peer group n=98, health professional group n=100)	NA	The first intervention lasted approximately 1 hour, the follow-up visits lasted 30 min.	As the visits progressed, the probability of adhering to treatment increased. Although differences were not significant, the group treated by a peer showed better results than the group treated by a health professional.
Simoni et al (2009)65	USA	Test the intervention effectiveness for adherence according to self-report and electronic drug monitoring, CD4 count and HIV-1 RNA viral load.	2×2 factorial randomised controlled trial	226 PLHIV (peer support n=57, pager n=56, peer and pager support n=56, usual care n=57)	NA	The 3-month peer support intervention consisted of 6 twice monthly 1 hour gatherings and weekly phone calls from peers to participants. The pager intervention included a message schedule to the participant’s daily medication regimen, which was confirmed by the clinical pharmacist. In addition to dose reminders, three other types of text messages were sent: educational, entertainment and adherence assessments.	The peer intervention was associated with greater self-reported adherence at immediate postintervention. However, these effects were not maintained at follow-up assessment; nor were the significant differences in biological outcomes. The pager intervention was not associated with greater adherence but was associated with improved biological outcomes at postintervention that were sustained at follow-up.
Yard et al (2011)75	USA	Assess whether patient factors moderated the impact of peer support and pager reminders on ART adherence and biological markers of HIV.	2×2 factorial randomised controlled trial	226 PLHIV (peer support n=57, pager n=56, peer and pager support n=56, usual care n=57)	NA	The 3-month peer support intervention consisted of 6 twice monthly 1 hour gatherings and weekly phone calls from peers to participants. The pager intervention included a message schedule to the participant’s daily medication regimen, which was confirmed by the clinical pharmacist. In addition to dose reminders, three other types of text messages were sent: educational, entertainment and adherence assessments.	None of 34 patient characteristics significantly moderated either intervention, suggest that intervention research might more profitably focus on other ways of improving effects, like individual patient needs, rather than target subgroups.
Simoni et al (2007)89	USA	Test the intervention effectiveness for viral load, adherence, social support and depressive symptomatology.	Randomised controlled trial	136 PLHIV (intervention group n=71, control group n=65)	NA	The 3-month peer support intervention consisted of six twice-monthly 1 hour group meetings at the clinic of all peers and actively enrolled participants in addition to weekly phone calls from peers to participants who were assigned to them individually by research staff on the basis of availability and presumed compatibility.	No between-conditions intervention effects on the primary outcome of HIV-1 RNA viral load or any of the secondary outcomes at immediate postintervention or follow-up.
Pearson et al (2007)64	Mozambique	Assess the efficacy of a peer-delivered intervention to promote short-term (6-month) and long-term (12-month) adherence to HAART.	Randomised controlled trial	350 PLHIV (intervention group n=175, control group n=175)	NA	Peers provided social support, information about the benefits and side effects of HAART, how to address stigma’s effect on adherence, and encouragement to participate in community support groups. The peers also provided an important link between the individual and other members of the HIV clinic team and the community.	Intervention participants, compared with those in standard care, showed significantly higher mean medication adherence at 6 months and 12 months. There were no between-arm differences in CD4 counts.
Boyd et al (2005)68	USA	Assess the effectiveness of the PC intervention for substance abusing (SA) rural women on adaptational outcomes important to HIV and AOD abuse: drugs of abuse, consequences of AOD use, motivation to change AOD use, perceived control of AOD use and ability to access AOD information/treatment (self-advocacy).	One arm pilot study	13 HIV+rural women	NA	The intervention was implemented in four counselling sessions over an 8-week to 12-week period. Each session lasted approximately 30–60 min.	Although limited by sample size, results suggest that this intervention was effective in helping women to acknowledge problems with their alcohol and drug abuse and to begin taking steps to achieve sobriety.
Øgård-Repål et al (2022)53	Norway	Explore how PLHIV experience the support provided by peers in outpatient clinics.	Qualitative study	16 PLHIV who aged 18 or older and had attended at least one peer support meeting	Face-to face individual interview	NA	The pre-determined categories constituted attachment, social integration, an opportunity for nurturance, reassurance of worth, guidance and safe place for peer support.
BHlthSc (2021)	Australia	Explore peer navigation from the perspective of practitioners with experience in treating PLHIV to understand the role they see for peer navigators in supporting PLHIV.	Qualitative study	6 medical practitioners	Telephone and face-to face individual interview	NA	HIV care was complex and need for additional resources for psychosocial care. They valued peer navigation as part of a patient support network and bridge to health and social care systems. HIV peers normalised HIV, alleviating fear and stigma, educating and translating clinical information for patients. However, the lack of awareness among clinicians, patient confidentiality and the absence of direct communication pathways with peer navigators were key challenges.
Sun et al (2020)51	China	Explore the experience of receiving peer support for treatment naïve PLHIV.	Qualitative study	17 PLHIV who participated in a peer support programme and showed good attendance adherence	Face-to face individual interview	NA	PLHIV acquired social support from peers including informational support, emotional support and instrumental support. PLHIV want diverse forms of peer support. PLHIV worry about exposing privacy during the project.
Sun et al (2019)74	China	Explore the experience of HIV peer supporters during a HIV peer support project.	Qualitative study	6 HIV peer supporters	Face-to face individual interview	NA	HIV peer supporters had advantages of providing support for PLHIV in terms of individual information support, emotional support and convenience. HIV peer supporters had benefits including improving self-management, psychological adjustment, acquiring a sense of self-worth and financial support. Negative impacts included risks of exposing privacy and emotional burnout.
Mantell et al (2019)55	Zimbabwe	Identify facilitators and barriers to peer-led community antiretroviral refill groups (CARGs) participation by HIV-positive men, with inputs from recipients of HIV care, community members, healthcare workers, donors and policymakers.	Qualitative study	147 PLHIV and 46 other stakeholders including community members, healthcare workers, donors and policymakers	20 focus group discussions and 46 key informant interviews	NA	Benefits of CARGs; challenges of CARGs; barriers to participation in CARGs: fear of stigma/confidentiality concerns, information gap, few perceived benefits; facilitators to participation in CARGs: better marketing of CARGs, provision of incentives (monetary and non-monetary), more flexibility in CARG design and implementation.
Monroe et al (2017)78	Uganda	Better understand the implementation, processes and results of a HIV peer support trial	Qualitative study	75 stakeholders including PLHIV, peer supporters and project staff	6 focus group discussions and 41 in-depth interviews	NA	Peer support improved information, motivation and behavioural skills, leading to increased engagement in pre-ART care. Situated factors included structural, clinical and environmental factors.
Li et al (2017)81	China	Understand the working experience of HIV peer educators.	Qualitative study	10 HIV peer educators	Face-to face individual interview	NA	Positive working experience: sense of achievement, sense of belonging and satisfaction from improved HIV/AIDS knowledge. Negative working experience: heavy workload and huge pressure, concern about exposing privacy, limited career development space and low salary.
Houston et al (2015)49	USA	Understand how participants perceive the role performed by peer facilitators.	Qualitative study	11 PLHIV who completed a peer-facilitated intervention	Face-to face individual interview	NA	Of the four types of social support (instrumental, informational, emotional and affiliational), most participants perceived informational and emotional support from their peer facilitators, followed by instrumental support. Affiliational support was the least frequently perceived type of social support.
Lee et al (2015)82	South Korea	Explore the experiences of peer supporters regarding their work in a home visit programme for people with HIV infection.	Qualitative study	12 HIV-positive peer supporters conducting home visits with PLHIV	Face-to face individual interview	NA	Six major themes emerged: feeling a sense of belonging; concern about financial support; facing HIV-related stigma and fear of disclosure; reaching out and acting as a bridge of hope; feeling burnout; and need for quality education.
de Souza et al (2014)80	Indian	Examine the various roles peer workers played in the context of HIV.	Qualitative study	31 HIV-infected peer workers engaged in providing counselling, outreach and health education to other people living with HIV	Face-to face individual interview	NA	Grounded analysis revealed five roles: role model, persuader, maven, going the extra mile and micro level advocacy.
Hallum-Montes et al (2013)83	USA	Investigate the barriers, challenges and facilitators to implementation of a peer integration programme.	Qualitative study	11 medical providers, 10 peers and 9 PLHIV	Individual semi-structured interviews	NA	HIV peers facilitate information exchange between patients and providers, and support patient retention and adherence. However, there is a lack of communication between peers and clinicians; HIV peers may also experience risk of emotional burnout for peers.
Mackenzie et al (2012)69	USA	Explores how HIV-positive injection drug users (IDUs) in a peer mentoring intervention articulated the effects of peer mentoring as a vehicle for change in their lives.	Qualitative study	68 HIV-positive heterosexually active IDUs who participated in the INSPIRE (Intervention for Seropositive Injectors - Research and Evaluation) study	Individual in-depth semi-structured interviews	NA	Five key themes are: construction of the peer mentoring identity; individual change; interpersonal or relationship change; community change; and challenges with the peer mentoring identity.
Dutcher et al (2011)48	USA	Examine from the perspective of peers the factors and activities that influence peer success with clients.	Qualitative study	23 HIV-positive peers	Individual in-depth interviews	NA	Peers reported that peer characteristics (HIV-status, common experiences and self-care) enable them to engage clients. Peers also required flexibility to respond to client needs, and their activities spanned four types of social support: informational, emotional, instrumental and affiliational.
Gusdal et al (2011)76	Ethiopia and Uganda	Exploring peer counsellors’ work and role in supporting patients’ adherence as viewed by the patients, the providers and the peer counsellors themselves.	Qualitative study	79 patients, 17 peer counsellors and 22 providers	Individual semi-structured interviews	NA	The first main category describes how peer counsellors played an important role by acting as role models, raising awareness and being visible in the community. They were also recognised for being close to the patients while acting as a bridge to the health system. The second main category deals with how peer counsellors found reward in helping others while at the same time acknowledging their limitations and need of support and remuneration.
Greene et al (2009)84	Canada	Highlight important methodological considerations for working with and supporting peer research assistants (PRAs) who are involved in doing community-based research.	Qualitative study	7 HIV-positive PRAs	Two in-depth focus groups	NA	Two important factors that need to be considered when developing research training; challenges and opportunities; safety and confidentiality; the benefits of peer research assistantships; revisiting the journey from scepticism to empowerment.
Hilfinger Messias et al (2009)72	USA	Explore HIV/AIDS PC from the perspective of women actively engaged in this work within the context of a community-based programme in rural areas of the southeastern USA.	Qualitative study	6 female PCs	Face-to face interviews	NA	Embodied work of HIV/AIDS peer counsellors is constructed around their personal identities and experiences. This work involves gaining entry to other HIV-positive women’s lives, building relationships, drawing on personal experiences, facing issues of fear and stigma, tailoring PC for diversity, balancing risks, and benefits and terminating relationships. Peer counsellors recognise the personal and collective value of their work, which, like much of women’s work within the context of family and community, lacks public visibility and acknowledgement.
Dickinson and Kgatea (2008)85	South Africa	Examine the relationship between involvement in peer education and stress.	Qualitative study	29 stakeholders: 15 workplace peer educators; 3 community peer educators; 3 group/project coordinators of the peer educators; 3 VCT counsellors working in the company hospital; and 5 people involved in training and support for the company’s new peer-educator programme	Individual semi-structured interviews	NA	Peer educators face many stresses in managing and supporting their own lives, thus their (voluntary) work as peer educators should not be taken out of context. Structural difficulties, skills deficiencies and other obstacles to effective communication with their peers can create stress.
Marino et al (2007)79	USA	Understand how HIV peers providing support may have affected PLHIV.	Qualitative study	9 HIV-positive peers	Individual interviews	NA	Four main themes: social acceptance, reciprocal support, personal growth and empowerment and resistance and other challenges.
Harris and Larsen (2007)54	Canada	Explore the benefits of peer support counselling from the perspective of PLHIV.	Qualitative study	12 PLHIV who have had experiences with PC	Individual interviews	NA	Participants identified several thematic benefits of PC for PLHIV and peer counsellors.
Messias et al (2006)73	USA	Elicit HIV/AIDS peer counsellors’ perspectives about delivery formats (face-to-face or telephone) for a counselling intervention.	Qualitative study	6 HIV peer counsellors	Individual in-depth interviews	NA	Peer counsellors identified personal contact as the major advantage of the face-to-face format. Personal contact afforded counsellors better opportunities to understand and assess clients’ physical, emotional and environmental status and allowed them to connect with peers in more concrete and personal ways. Being physically present was also a very direct and effective way to role model for other HIV positive women. Peer counsellors identified a number of inherent barriers and challenges to telephone interventions but also recognised potential logistic and personal advantages.
Karver et al (2022)77	Dominican Republic	Describe the role of peer navigation and support on enhancing the quality of HIV treatment and care services experienced by female sex workers (FSWs).	Mix-method study	211 FSWs living with HIV (survey data); two rounds of in-depth interviews (n=20 per round)	Individual in-depth interviews	NA	Peer navigation and support was instrumental in assisting FSWs linkage to HIV care after diagnosis, elevating FSWs’ ability to access more comprehensive clinical care facilities and promoting agency by improving FSWs’ skills to more strategically and effectively engage with the clinical environment and healthcare providers. Peer navigation was positively associated with experiencing more respectful treatment by clinical staff and greater satisfaction with overall HIV care services.
Steward et al (2018)86	South Africa	Assess acceptability and feasibility and characterise the mechanisms of action for a HIV peer support programme.	Mix-method study	25 PLHIV (survey data); 10 PLHIV, 4 navigators and 5 clinic providers for interviews	Individual in-depth interviews	NA	HIV stigma emerged as a primary driver of barriers to care. Navigators helped clients overcome feelings of shame through education and by modelling how to live successfully with HIV. They addressed discrimination fears by helping clients disclose to trusted individuals. These actions, in turn, facilitated clients’ care engagement, ART adherence and HIV prevention efforts.
Kemp et al (2016)67	South Africa	Qualify and quantify the impact of the structured support group intervention known as Integrated Access to Care and Treatment (I ACT), as implemented by a small community-based organisation in rural South Africa, on clients’ knowledge, attitudes and practice regarding HIV/AIDS, including their experiences of stigma, willingness to disclose and uptake of and adherence to treatment services.	Mix-method study	66 PLHIV (pre/post-test data); 17 PLHIV (interviews)	Individual in-depth interviews	NA	Paired t-tests did not detect significant changes in the main outcomes. Qualitative results suggested a psychosocial benefit as participants connected with their peers, expressed themselves openly and re-engaged with their communities.
Peterson et al (2012)50	USA	Describe the various forms and functions of peer support for PLHIV; validate the Dennis10 concept analysis of peer support within health contexts.	Mix-method study	81 PLHIV who had some experience with peer social support	One-on-one interviews	NA	Peer support is a potentially important adjunct to clinical care for enhancing coping skills, thereby improving the psychosocial functioning of PLHIV. It is important to assess patient access to peer support; provide opportunities for peer support in the clinical setting; and enhance disclosure and support-seeking skills to facilitate this benefit.
Safren (2011)	UK	Evaluate the acceptability and feasibility of a peer-driven IMB (information-motivation-behavioural skills) intervention designed to reduce HIV sexual risk behaviours among MSM in primary care.	Mix-method study	195 PLHIV (survey data); 17 PLHIV (interviews)	Individual in-depth interviews	NA	Of those who entered the intervention and completed the initial intake, 62% completed all four of the intervention sessions and 93% completed at least one. While there was no overall change in transmission risk behaviour (TRB) for the whole sample, among those who reported HIV TRB at baseline (n=29), there were significant reductions in TRB over the next year. Themes that emerged in qualitative exit interviews conducted with a subset of participants centred on peer counsellor quality, intervention implications and intervention experience.
Arem et al (2011)56	Uganda	Better understand processes of a cluster-randomised trial on the effect of PHWs on AIDS care.	Mix-method study	Qualitative methods involved patients, PHWs and clinical staff and included 38 in-depth interviews, 8 focus group discussions and 11 direct observations. Quantitative methods included staff surveys, process and virological data analyses.	38 in-depth interviews, 8 focus group discussions and 11 direct observations	NA	Task shifting to PHWs positively affected structural and programmatic functions of care delivery—improving clinical organisation, medical care access, and patient–provider communication—with little evidence for problems with confidentiality and inadvertent disclosure.
Pearson et al (2006)70	Mozambique	Describe the experiences of creating and implementing a scaled-up version of a modified directly observed therapy (mDOT) programme for PLHIV starting HAART.	Mix-method study	350 PLHIV including 174 were randomised to mDOT		NA	Key components of the intervention’s success included using peers who were well accepted by clinical staff, adequate training and retention of peers, adapting daily visit requirements to participants’ work schedules and physical conditions and reimbursing costs of transportation.
Aung et al (2021)66	Myanmar	Examine differences in HIV knowledge, stigma, ART adherence, barriers to care, social support satisfaction and attitudes related to counselling, among PLHIV who received peer counsellor compared with those who received standard counsellor.	Cross-sectional study	1006 PLHIV	NA	NA	Compared with standard counsellor, peer counsellor participants had lower enacted stigma, mean internalised stigma and risk of ART non-adherence, while reporting higher levels of barriers to care.
Chime (2019)	Nigeria	Compared the level of self-stigma among PLHIV in peer support and non-support groups.	Cross-sectional study	804 PLHIV	NA	NA	Though peer support groups may be a starting place for the development of social support interventions for PLHIV, it might not be sufficient to combat self-stigma. Interventions aimed at economic empowerment of PLHIV and public enlightenment are essential for effective mitigation against self-stigma.
Tobias et al (2010)71	USA	Describes the results of a survey on peer roles and knowledge.	Cross-sectional study	186 HIV-positive peers	NA	NA	Peers perform a wide range of roles, including assistance with care and treatment, emotional support and service referrals. PLHIV for more than 5 years, in paid employment with more than a high school education had higher HIV knowledge scores than volunteers. Higher education, length of time living with HIV, age and speaking English as the primary language were associated with higher peer knowledge scores.
Campbell (2008)	USA	Determine if patients who are peer-mentored at their intake examination remain in care longer and attend more physicians’ visits than those who were not mentored.	Cohort study	1639 PLHIV	NA	NA	Patients who had a mentor at intake were more likely to return for primary care HIV visits at 90 and 180 days. Mentored patients also were more likely to be prescribed ART within 180 days from intake. Other risk factors that impacted remaining in care included gender, previous care status, time from diagnosis to intake visit and intravenous drug use. Clinical health outcomes did not differ significantly between groups.

ADR, adverse drug reaction; AOD, alcohol and other drug; ART, antiretroviral therapy; BCP, basic care package; HAART, highly active antiretroviral therapy; HRQoL, health-related quality of life; MSM, men who have sex with men ; PLHIV, persons living with HIV; VCT, voluntary counselling and testing.