SUMMARY It is increasingly recognized that global goals for HIV epidemic control cannot be realized without improving retention in HIV care and adherence to antiretroviral therapy (ART). Only 58% of people living with HIV (PLHIV) in eastern and southern Africa are virally suppressed, and adherence counseling provided to those with elevated viral loads results in viral suppression only 40-50% of the time. Financial incentives, first used for poverty reduction, have been shown to motivate behavior change and improve engagement in HIV-related services. However, there is a paucity of data about the effectiveness of incentive-based programs for people who have disengaged from HIV care as well as the proactive use of incentives for PLHIV struggling with adherence. This research gap limits our understanding of whether financial incentive programs are worthwhile investments to support lifelong care, which is essential to the success of ‘treatment as HIV prevention’ (TasP). The proposed research will advance global knowledge about the effectiveness of financial incentives for strengthening the continuity of HIV care. We will build on data from a pilot study we conducted in Tanzania which found that an intervention offering a one-time financial incentive to out-of-care PLHIV was feasible, acceptable, and preliminarily efficacious at motivating re-engagement in HIV care. Leveraging our established research program and expertise with behavioral economics, we designed a 5-year, mixed-methods, hybrid effectiveness-implementation study to evaluate the financial incentive intervention and describe its successful implementation, with the ultimate goal of closing the gap towards achievement of UNAIDS’ ‘95-95-95’ goals. We will first assess if a one-time financial incentive improves re-engagement in care and durable viral suppression at 12 months among 640 PLHIV in Geita and Kagera Regions who have disengaged from care (Aim 1). We will then measure the effectiveness of short-term financial incentives offered to 692 in-care PLHIV who are at risk of loss to follow-up or poor adherence, with durable viral suppression at 12 months as the outcome (Aim 2). A mixed-methods study will describe implementation successes and challenges and synthesize lessons learned to inform adoption of incentive programs for vulnerable PLHIV (Aim 3). The project is a collaboration of the University of California, Berkeley, Health for a Prosperous Nation, Rasello, Management and Development for Health, and the Tanzania Ministry of Health, Community Development, Gender, Elderly, and Children. At the conclusion of the project, we will have rigorously evaluated the incentive strategy and will understand whether it can mitigate the persistent challenge of disengagement from HIV care, consistent with NIH Office of AIDS Research priorities for implementation research on retention in care and adherence to ART. This information is highly relevant to the spectrum of incentive-based programs being imp...