Transgender men and transmasculine people—those who identify as men or masculine and were assigned female at birth—have not been centered in HIV prevention efforts until recently [1-3]. Transgender people, who comprise an estimated 1.4 million US adults, are identified as a key population in the 2021-2025 US National Strategic Plan to end the HIV epidemic [4,5]. In a 2019 meta-analysis, HIV prevalence among transgender men in the United States was 3.2%—10 times greater than in the general US population [6]. Many transgender men and transmasculine people are men who have sex with men (TMSM) and engage in sexual activity with cisgender (cis) males and with partners of other genders who have a penis [7]. TMSM, especially those who engage in condomless genital or anal sex or who share needles for illicit drug use and hormones, are at risk for HIV and require tailored HIV prevention strategies [8-11]. However, no efficacious HIV prevention interventions currently exist for this population [1]. Research is needed to develop interventions that facilitate access to biobehavioral HIV prevention for at-risk TMSM, particularly those in geographic hot spots with a high HIV epidemic burden [4].

TMSM require HIV prevention services that address their unique situated vulnerabilities and gender affirmation needs [12]. Most TMSM have not undergone genital surgery and may engage in receptive genital and anal sex, which often goes unreported to sexual health providers [8,13]. Gender nonaffirmation from cis male sexual partners is common and is associated with behavioral risk for HIV acquisition in TMSM [14]. TMSM also express concerns about concomitant preexposure prophylaxis (PrEP) and testosterone use for medical gender affirmation, which may reduce interest in and uptake of PrEP among TMSM with HIV behavioral risk [15]. Finally, TMSM are at increased risk of mental health morbidity (eg, depression, substance use), which is associated with HIV risk [7]. However, TMSM face barriers to accessing HIV prevention services, and tailored services remain lacking [15]. These barriers include discrimination that leads to care avoidance, misconceptions that TMSM are not at risk for HIV, and logistical challenges such as scheduling medical appointments [14-16]. The noninclusion of TMSM in PrEP trials and promotion further deters their use of PrEP [1]. Thus, effective HIV prevention for TMSM will need to remove barriers to care and address gender affirmation needs, while also building awareness, motivation, and behavioral skills necessary to prevent HIV among all transgender and MSM populations [17-19].

Evidence-based peer strategies that empower communities through social support, stigma reduction, and skills building are widely accepted in transgender communities [20-23]. Peer navigation interventions are individualized, using 1-on-1 sessions led by trusted peers with shared lived experiences. Peer navigation has demonstrated success in improving outcomes among people with HIV [24-32], including transgender women [33-35]. It has also been effective in increasing PrEP uptake and adherence [36-38], and shows promise for transgender women [37,39]. While peer navigation is endorsed by TMSM [17], no interventional efficacy research has yet been conducted.

Our team has previously adapted and implemented peer navigation interventions for transgender communities to increase linkages to health care services. This includes the Gender-Affirming Clinical and Public Health Model at Fenway Health (Fenway), which employs individualized 1-on-1 peer health navigation to support care engagement [32,40]. Peer health navigation typically involves 4 structured sessions over 6 months of follow-up, and evaluation of Fenway’s program has demonstrated high feasibility and acceptability, with increased health care engagement outcomes within 60 days [41]. One-on-one sessions incorporate goal setting, skills building, assessment, planning, and navigation. Peer navigation has also been shown to increase linkage to medical, behavioral, and HIV prevention services (eg, PrEP) [41,42]. The Fenway peer navigation model has been disseminated nationally [43] and digitally [44]. Our team further replicated peer navigation with transgender people in Peru for HIV prevention [45], highlighting its adaptability, utility, and broad transferability.

Another evidence-based HIV prevention strategy used in transgender communities is group-based peer interventions, which involve peer-facilitated group sessions [20,21,23,46]. A pilot study of LifeSkills for Men (LS4M) [20], a small group–based behavioral intervention designed to reduce HIV risk and the mental health effects of stigma in TMSM, found high acceptability and positive trends in health outcomes. LS4M was adapted from LifeSkills [21], an efficacious intervention for transgender women. The LS4M curriculum consisted of 8 hours of content delivered across 4 weekly sessions. The pilot demonstrated that LS4M was feasible, highly acceptable, and associated with promising improvements over 4 months of follow-up, including increased transgender support and reductions in mental health severity, sexual risk, and gender nonaffirmation [20].

Evidence supports peer-delivered interventions for HIV prevention; however, few studies have compared individual and group formats or evaluated combined delivery [47,48]. Research is needed to assess the individual and combined effects of 1-on-1 and group-based peer-delivered strategies. Individualized interventions are tailored to the specific needs of TMSM, while group-based interventions affirm TMSM not only as individuals but also collectively as members of a community.

Three conceptual frameworks informed the study (Figure 1). First, the Healthcare Accessibility Framework [49] highlights systemic and population-specific barriers to HIV prevention for TMSM, such as avoidance of care due to stigma, misconceptions that transgender men are not at risk for HIV, perceived difficulty navigating PrEP logistics [14-16], and the need for additional services (eg, mental health). It also emphasizes facilitators of access, such as health care empowerment [50]. Second, the Gender Affirmation Framework [7,51] underscores that being affirmed in one’s gender is a key health determinant and that gender affirmation is not “one-size-fits-all.” Many TMSM do not have or want genital surgery and are therefore at increased risk of HIV when engaging in receptive anal and vaginal sex [8,13]. Stigma and gender nonaffirmation also negatively affect HIV risk-taking and PrEP decision-making [14,52]. Gender-affirming HIV prevention that addresses TMSM-specific vulnerabilities is essential. Third, the Information, Motivation, and Behavioral Skills (IMB) model [53] is an evidence-based behavior change framework that targets increasing information (eg, PrEP knowledge), motivation (eg, attitudes, perceived benefits/risks), and behavioral skills (eg, self-efficacy) for TMSM. Effective HIV prevention for TMSM must integrate health care access, gender affirmation, and IMB constructs [17-19].

The goal of the Transmasculine One-on-One and Group Empowerment for Targeted HIV Reduction (TOGETHR) study was to evaluate the effectiveness of digitally delivered individual and small-group peer-based strategies in improving PrEP uptake and adherence among at-risk, HIV-negative adult TMSM.

Applying the Healthcare Access [49], Gender Affirmation [7,51], and IMB [53] frameworks, we conducted a digital, open-label, randomized 2×2 factorial trial (1:1:1:1 allocation) of peer-delivered HIV prevention strategies to increase PrEP uptake among TMSM (n=300) residing in Ending the HIV Epidemic (EHE)–prioritized geographic hot spots in the United States. The specific aims were to:

The TOGETHR study was a collaboration between the University of Michigan and The Fenway Institute at Fenway Health. The Fenway Institute led study management, including recruitment and retention, enrollment, intervention implementation, and data collection. The University of Michigan was responsible for data analysis. Investigators from Johns Hopkins University, Duke University, Drexel University, and the University of California, Los Angeles also contributed to the study.

TOGETHR was a digitally delivered, open-label, randomized 2×2 factorial trial of peer-delivered HIV prevention strategies. The design included 2 factors: individualized 1-on-1 peer navigation (PrEP4T vs none) and group-based behavioral intervention (LS4TM vs none). The primary outcome was PrEP uptake, confirmed biologically. Secondary outcomes were PrEP adherence, defined as tenofovir diphosphate (TFV-DP) concentrations >700 fmol/punch (corresponding to >4 doses per week) [54], and PrEP persistence, defined as 2 consecutive dried blood spot (DBS) measures indicating PrEP use. Participants were randomized 1:1:1:1 to the 4 study conditions, with stratification by ethnoracial identity (Black, Indigenous, and People of Color [BIPOC] vs White non-Latine) and by Movement Advancement Project (MAP) state lesbian, gay, bisexual, transgender, and queer (LGBTQ) equality policy tally (“high, medium, or fair” vs “low or negative”) [55]. The enrollment target was approximately 50% BIPOC participants. The study protocol was developed in accordance with the 2025 Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) guidelines to ensure methodological rigor, transparency, and completeness in trial reporting [56].

TOGETHR was funded by the National Institutes of Health (NIH; R01MH129175). On March 21, 2025, however, the NIH prematurely terminated the grant, citing its focus on “gender identity.” The justification given was that, under the Trump administration (commencing January 20, 2025), “it is the policy of NIH not to prioritize such research programs." In April 20205, the American Civil Liberties Union (ACLU), Protect Democracy, and the Center for Science in the Public Interest filed a lawsuit on behalf of researchers, the American Public Health Association (APHA), and others challenging the abrupt termination of research grants on disfavored topics and populations by NIH. The current grant was included in the lawsuit. The grant was re-instated on July 9, 2025; however, litigation is ongoing and the future of the project remains uncertain [57].

Inclusion criteria were (1) age ≥18 years; (2) assigned female sex at birth and identified as a “man, transgender man, or transmasculine”; (3) had sex in the past 3 months with a partner who had a penis and was assigned male sex at birth; (4) access to a smartphone or computer with internet; (5) HIV-negative at baseline (confirmed); (6) reported behavioral HIV risk in the past 3 months, including at least one of the following: (i) receptive vaginal/frontal or anal sex with an assigned male sex at birth partner with a penis; (ii) sharing needles or syringes for illicit drug use or hormones; (iii) self-reported sexually transmitted infection diagnosis; (7) residence in a US EHE-targeted geographic hot spot (48 counties, Washington, DC, San Juan, Puerto Rico—where >50% of HIV diagnoses occurred in 2016-2017—or 7 states with substantial rural HIV diagnoses; see Table S1 in Multimedia Appendix 1); (8) willing and able to provide informed consent in English; and (9) comfortable reading and conversing in English.

TOGETHR employed a participatory population approach, working with—rather than on—the TMSM community [58]. The study focused on peer-delivered interventions, with peers defined as “transgender men or transmasculine individuals.” Multiple investigators, all research staff interfacing with participants, and all intervention facilitators were transmasculine. A virtual community advisory board (CAB), composed of TMSM, was convened at study inception and met monthly or bimonthly via Zoom (Zoom Communications, Inc). CAB members received an honorarium for their time. The CAB played a central role in the research, collaborating closely with the study team on all aspects of the trial and serving as an essential mechanism for community consultation. The CAB provided extensive input on the interventions, study protocols and procedures, privacy and confidentiality safeguards, implementation and evaluation processes, recruitment and retention activities, dissemination strategies, and troubleshooting challenges to ensure acceptability for TMSM.

Participants were recruited and enrolled virtually nationwide from US EHE jurisdictions [5]. Recruitment strategies included social media (eg, closed Facebook groups, Reddit), community networking platforms (eg, Lex), paid advertisements and posts on geosocial networking dating apps (eg, Grindr), outreach through transgender health care, social, and advocacy organizations (eg, listservs, events), and peer-to-peer networks (eg, referrals from research staff, the CAB, and enrolled participants). Recruitment materials (eg, flyers, text, images, advertisements, taglines) were designed to support purposive sampling, such as geotargeting and incorporating diverse images of BIPOC and Latine MSM. Flyers and web-based advertisements directed potential participants to the study web page, where they could complete a screening form or contact the research team directly via email.

For retention, the study team collected and regularly updated participants’ contact information (eg, email, phone, mailing address, and Facebook or Instagram handles), along with the contact details of 1-3 individuals who could help locate them if needed. Participants were contacted through their preferred communication method to receive study visit reminders. Enrollment and retention were tracked in REDCap (Research Electronic Data Capture; Vanderbilt University), a secure, web-based, Health Insurance Portability and Accountability Act (HIPAA)–compliant system.

Potential participants first completed a digital screener to assess preliminary eligibility. Those deemed eligible were scheduled for a virtual enrollment visit via Zoom with study staff. After eligibility was confirmed, participants completed a written informed consent process. Individuals who consented were conditionally enrolled and then completed a baseline survey and a DBS home collection kit for HIV and PrEP testing (described below). Participants who confirmed HIV negativity were fully enrolled.

After participants received eligible HIV test results, they were randomized, and study staff informed them of their assigned condition and scheduled any intervention sessions. Following communication of HIV results and randomization, all participants received an email with a password-protected link to the SOC materials housed on the study website.

Participants completed online surveys at baseline and at 3, 6, 9, 12, 15, and 18 months (Figure 2). Comprehensive surveys, lasting approximately 30 minutes, were administered at baseline, 3, 6, 12, and 18 months. The 6-month survey also included an assessment of the intervention program completed after intervention delivery. Short surveys, focused on PrEP uptake and adherence and lasting about 15 minutes, were administered at 9 and 15 months. All surveys were hosted on REDCap, a HIPAA-compliant platform.

Survey measures were guided by the Healthcare Accessibility [49], Gender Affirmation [7,51], and IMB [53] frameworks. Validated measures from transgender populations and prior research were selected to ensure comparability [59-62]. Baseline surveys included both lifetime and past 3-month recall, while follow-up surveys assessed past 3-month recall only. Domains assessed included demographics (age, race, ethnicity, gender identity, sexual orientation, education, income, housing, health insurance), gender affirmation (social, medical, legal), and unmet gender affirmation needs [59,61]. Measures included the PrEP cascade (awareness, indications, uptake, adherence, and persistence, including both daily oral and long-acting injectable formulations) [15,62]; barriers and facilitators to PrEP care [8,62]; PrEP knowledge, motivations, and preferences [8,15,63]; PrEP self-efficacy [64]; and PrEP empowerment [65]. Behavioral risk for HIV acquisition was assessed through sexual partners and practices using an adaptation of the Transmasculine Sexual Health Assessment [66], as well as injection drug use, needle-sharing behaviors, and perceived HIV risk [62]. Sexual partner communication and affirmation were measured using the Sexual Communication Self-Efficacy Scale [67] and the Gender Non-Affirmation from Sexual Partners Scale [14], respectively. Additional questions addressed HIV testing outside the study and sexually transmitted infection screening and diagnoses [61]. Mental health measures included psychological distress (Kessler-6) [68], posttraumatic stress disorder symptoms (Primary Care Posttraumatic Stress Disorder Screen) [69], resilience (Brief Resilience Scale) [70], and use of mental health services (eg, psychotherapy, support groups). Alcohol use disorder was assessed with the Alcohol Use Disorders Identification Test—Consumption [71], substance use disorder symptoms with the Drug Use Disorder Identification Test—Consumption [72], along with categories of drugs used. Discrimination was measured using the Everyday Discrimination Scale [73], which included 14 possible attributions (eg, age, gender identity, race, ethnicity). Internalized stigma [61] was also assessed. Additional measures included health care empowerment [74], health care access, utilization, and mistreatment in health care settings [60]. Social support was assessed with a short form of the Social Support Questionnaire [75], the Trans Community Connectedness subscale of the Gender Minority Stress and Resilience Measure [76], and metrics of social network size [61].

The primary outcome was biomarker-confirmed PrEP uptake, assessed via emtricitabine triphosphate (FTC-TP) and tenofovir diphosphate (TFV-DP) concentrations in DBS. FTC-TP/TFV-DP assays were used for TFV-containing PrEP regimens approved for this population. PrEP uptake was defined as the detection of any quantifiable drug concentration. Secondary outcomes were PrEP adherence, indicated by TFV-DP concentrations >700 fmol/punch (corresponding to ≥4 doses per week) [54], and PrEP persistence, defined as 2 consecutive DBS samples showing PrEP use. Thresholds were based on the emtricitabine/tenofovir disoproxil fumarate (F/TDF) regimen and adjusted as appropriate for participants using other TFV-containing PrEP formulations (eg, emtricitabine/tenofovir alafenamide, F/TAF).

Participants self-collected DBS samples for HIV testing and PrEP level assessment at baseline, 6, and 12 months. Biospecimen processing was conducted by Molecular Testing Lab (MTL), a CAP-accredited and Clinical Laboratory Improvement Amendments–certified laboratory specializing in at-home specimen collection and processing. Participants provided a mailing address, which was validated through the US Postal Service Address Information application programming interface, and home specimen collection kits were shipped via the US Postal Service. Each kit included detailed visual instructions for specimen collection and a prepaid return mailer. Video instructions were available on the study website to guide participants through specimen self-collection. Each kit included a finger stick device, alcohol wipe, adhesive bandage, a Whatman 5-spot DBS card for HIV testing, and a Whatman 2-spot DBS card for PrEP adherence testing. Participants collected their specimens and returned the cards to the laboratory using the self-addressed, stamped envelope provided in the kit.

MTL conducted a fourth-generation HIV-1 antigen/antibody ELISA to detect HIV p24 antigen, HIV-1 (groups M and O) antibodies, and HIV-2 antibodies in human blood (sensitivity 100% and specificity 100%) (Molecular Testing Labs, unpublished data, December 2020). Biologic measures of PrEP uptake and cumulative adherence were performed only for participants who self-reported recent PrEP use. HIV test results were typically available within 14 days via the secure MTL portal, reviewed by study staff, and then shared with participants. Positive HIV results were communicated by designated clinical staff, who also contacted participants with positive DBS results to facilitate confirmatory testing. Participants with negative confirmatory results remained eligible for enrollment. PrEP levels were not reported to participants.

All participants received US $30 for each comprehensive survey completed (baseline, 3, 6, 12, and 18 months) and US $10 for each short survey completed (9 and 15 months). Participants received US $20 for each self-collected HIV/PrEP test kit completed at baseline, 6, and 12 months. Participants in the PrEP4T and LS4TM arms received US $10 for each intervention session attended (6 sessions per intervention). The total compensation for participants was as follows: condition A (SOC; US $250); condition B (PrEP4T; US $310); condition C (LS4TM; US $310); and condition D (PrEP4T + LS4TM; US $370). Participants completing a qualitative interview at 9 months received an additional US $50.

Participants were compensated using ClinCard, a reloadable debit card that allowed study staff to add funds via an online portal as study activities were completed. ClinCards were mailed directly to participants’ preferred addresses after study enrollment.

In the final 6 months of this 5-year study, PrEP4T and LS4TM were offered to all participants regardless of study group assignment to gather implementation data; no compensation was provided during this period.

A subset of 40 TMSM, stratified by PrEP use, was to be purposively selected for IDIs (10 per study arm) at their 9-month visit. Sampling aimed to ensure that 50% of participants were BIPOC or Latine. Additional participants could be recruited as needed to achieve data saturation. IDIs were conducted as part of the 9-month study assessment—the acute postintervention time point—to maximize recall. IDIs explored participant decision-making and experiences with PrEP and the interventions. Interviews were conducted via an online video-conferencing platform (Zoom) [87]. Each IDI lasted approximately 60-90 minutes, followed a semistructured interview guide (Multimedia Appendix 2), and was to be conducted by an interviewer trained in qualitative research and experienced in working with transgender communities.

Participants were randomized after their baseline HIV results were received and confirmed. Randomization was automated, computer-generated, and allocation sequences were concealed. Stratification was based on ethnoracial identity (BIPOC or Latine vs White) and MAP state LGBTQ equality policy tally (“high, medium, or fair” vs “low or negative” overall policy tally, as of October 2023; see Table S2 in Multimedia Appendix 1) [55]. The MAP state LGBTQ equality policy tally assesses over 50 LGBTQ-related laws and policies across US states (eg, nondiscrimination, health care access, religious exemptions, identity documents), providing a snapshot of the legal and policy climate for LGBTQ people [55]. Stratification was implemented to ensure balance across study arms and to facilitate subgroup analyses [88], given the disproportionate HIV burden among BIPOC or Latine versus White individuals [5] and the impact of repressive anti-LGBTQ policies on HIV prevention efforts [89]. Blinding was maintained at the statistician and investigator levels [90], but was not possible for participants or intervention staff.

All research staff completed extensive training on the study objectives, protocol, and intervention procedures. Additional training covered transgender health, HIV, PrEP navigation, mental health crisis management, substance use, harm reduction, trauma-informed care, and addressing experiences of violence. Intervention staff training included observing and conducting mock intervention sessions. A mental health clinician, who was both a consultant and a member of the community, was available on-call to provide regular clinical supervision. Staff were also trained in human participant protections, confidentiality and privacy, informed consent, and Good Clinical Practice in accordance with federal regulations. Refresher training was conducted annually. Laboratory testing followed standardized protocols and procedures. Surveys were administered using computer-assisted self-interview methods to ensure consistency and reduce social desirability bias. Instruments were piloted to maximize comprehension, and logic checks and skip patterns were employed to minimize data entry errors. Data were reviewed regularly to ensure consistency and accuracy.

To ensure interventions were implemented as intended and core components were delivered according to protocol, intervention facilitators completed a checklist documenting their self-rated adherence to the intervention procedures. Session notes captured qualitative data on intervention implementation, including facilitator rapport, group dynamics, and other insights related to delivering manualized interventions. At the 6-month follow-up survey, participants reported on the intervention content they received and their experiences, including responses on the 8-item Client Satisfaction Questionnaire [91].

The Fenway Institute at Fenway Health served as the single institutional review board of record (institutional review board protocol approval number 2023-12). Written informed consent was obtained from all participants before initiating any study procedures. Extensive safeguards were implemented to protect participant information and ensure privacy and confidentiality, including storing participant names and contact information separately in password-protected files from deidentified survey data and HIV testing results. The study was protected by a Certificate of Confidentiality from the NIH. Participants were compensated for their involvement (see the “Incentives and Disbursement” section). A Data Safety and Monitoring Board was established to oversee the trial’s progress, review safety data, and provide recommendations on whether the trial should continue based on its assessment of safety and research performance. The board convened at least annually.

Recruitment and enrollment began on February 1, 2024. Cumulative recruitment and enrollment numbers from February 2024 to March 2025 are shown in Figure 3. Recruitment activity types are represented by colored dashed lines, while completed screeners and completed baseline surveys are shown as solid orange and blue lines, respectively.

Granger causality tests were conducted to forecast screening and baseline enrollment survey completions based on recruitment activity types (Table 4). The most effective strategies for 2-week baseline survey completions were closed Facebook groups (F_2,23=6.52, P=.006) and Lex (F_2,23=4.63, P=.02). Lex also significantly predicted screening completions at both 1 week (F_1,26=10.41, P=.003) and 2 weeks (F_2,23=6.18, P=.007).

As of March 20, 2025, 103 TMSM were enrolled (Table 5). The median age was 26 (IQR 24-31) years. Among the 103 participants, 39 (37.9%) identified as BIPOC and 18 (17.5%) identified as Latine. The most frequently reported gender identities were “transgender men or trans man” (36/103, 35%); transmasculine (31/103, 30.1%); and nonbinary, genderqueer, or gender nonconforming (15/103, 14.6%). The majority of participants had socially, legally, and medically affirmed their gender identity. Participants reported diverse sexual orientation identities, with 67 (65%) identifying as queer, 38 (36.9%) as bisexual, 37 (35.9%) as gay, and 18 (17.5%) as pansexual (totals exceed 100% due to a “select all that apply” response format). The sample was highly educated: 69 (67%) had a 4-year college degree or higher, and 24 (23.3%) were full-time students. A small proportion (7/103, 6.8%) reported having no health insurance.

This digital factorial trial aimed to compare the efficacy of online 1-on-1 peer navigation (PrEP4T), online peer-delivered small group–based behavioral intervention (LS4TM), a combination of 1-on-1 and group-based interventions (PrEP4T + LS4TM), and an SOC in increasing PrEP uptake and adherence among TMSM in HIV epidemic priority hot spots nationwide. It represents the first full-scale efficacy trial of peer-delivered interventions with TMSM. The study also sought to enhance understanding of the pathways linking health care access, gender affirmation needs, community connectedness, and PrEP uptake and adherence in TMSM, with potential applicability to other transgender populations. This study was part of a critical research pathway aimed at identifying strategies to prevent HIV acquisition in TMSM, a population historically underserved in HIV prevention. Key lessons include the essential role of community participation through the CAB and the effectiveness of social media and community networking platforms for recruiting and engaging this population. Findings from this study can inform future trials of HIV prevention packages in which peer-delivered interventions are a core component.

Several limitations of this study should be noted. First, although the study was conducted nationwide, participants were drawn from EHE jurisdictions, limiting generalizability to the broader US population. Second, as a fully digital trial, participants were required to have access to a smartphone or computer with internet connectivity. This may have led to undercoverage of the source population and the unintentional exclusion of individuals with limited resources, restricted digital access, or intermittent technology access—groups who may also be at risk for HIV acquisition. Finally, this study cannot fully disentangle the effects of the intervention content from the additional time spent with peer navigators in the combined group. Nevertheless, the trial addresses a critical research gap by comparing individual versus group formats and evaluating the combined effects of both approaches within an at-risk and underresearched HIV epidemic population [47,48].

This novel study aimed to address an urgent gap in HIV prevention research for an underserved and priority population at risk in the HIV epidemic. Close collaboration and partnership with the TMSM community, along with extensive community engagement activities, were central to the study’s success and provided valuable lessons for future HIV prevention research and practice with this population. Findings may also inform digital, peer-based HIV prevention strategies for other vulnerable populations affected by the HIV epidemic.