An intervention integrating peer navigation and family engagement to improve ART and OST adherence in South Africa - Project Abstract Injection drug use is expanding and may compromise progress in achieving the 95-95-95 goals in South Africa, an already high HIV burden setting. At this time, there is 11.4-58.4% HIV prevalence range for people who inject drugs (PLWHID) with less than half adherent to antiretroviral therapy (ART) and virally suppressed. Despite established clinical guidelines for ART and opioid substitution therapy (OST) and harm reduction strategies, retention in treatment remains low. Our current ART-OST program provides free access to both treatments with recruitment and referral being led by peer navigators at Yeoville Clinic in the City of Johannesburg, South Africa. A clinic is located high population density setting and serves a low-income community with overlapping vulnerabilities like trauma and drug use. Over the last four years, 3021 PLWHIDs were initiated on ART, OST, or ART-OST, but the 12-month retention was low at 26%, 30%, and 31% respectively. Process evaluation outcomes showed that peer navigation alone may not be enough to support treatment outcomes, but PLHWID preferences for additional family engagement may address a support gap. Building upon our established ART- OST program infrastructure in Johannesburg, South Africa, we will assemble evidence-based practices for family-engaged interventions and enhanced training for peer navigators to deliver the intervention for ART and OST support, and then assess its preliminary impact in improving ART adherence and OST continuation. The intervention is called Project Vuselela (PV), meaning Restore in isiZulu. Our intervention will be guided by Social Action Theory and Information-Motivation-Behavior model. In Aim 1, we will develop PV guided by the Intervention Mapping model. We will assemble evidence-based practices for peer navigation and family engagement; interview PLWHIDs, family members and service providers to identify preferences for intervention content and delivery; and then establish implementation protocols and measures for fidelity and behavior change. Intervention development will be guided by a community advisory board. In Aim 2, we will pilot-test PV using randomized controlled trial design. PLWHIDs will be recruited who are newly engaged in ART and OST services. We will assess ART adherence and OST continuation (primary outcomes) at 3- and 6-months. If PV shows trending effectiveness, we will conduct an efficacy trial of the intervention that may be scaled to improve PLHWID HIV and OST outcomes in similar settings where injection drug use is expanding.