PROJECT SUMMARY This five-year K01 Mentored Research Scientist Development Award will provide Dr. Rucinski with the mentorship and training to become an independent investigator focused on research that optimizes the health and well-being of women and girls at high risk of HIV acquisition and transmission in sub-Saharan Africa. Training is at the foundation of this proposal and comprises mentorship with expert and multi-disciplinary implementation science (IS) researchers, didactic coursework, experiential learning, meetings with key HIV and stakeholders and community leaders, and rigorous mentored research. The following training objectives will be accomplished during this award: (1) Obtain scientific expertise in the concepts, theories, tools and methods used to advance HIV-related IS research and practice; (2) Develop comprehensive skills in qualitative research methods to support the application of mixed-methods approaches for HIV-related IS research; and (3) Acquire content expertise in adolescent health and development to inform the tailoring, adaptation, and testing of developmentally appropriate sexual and reproductive health services for adolescents and young adults. Supported by these objectives, the proposed mentored research project will generate a tailored packaged of implementation strategies to strengthen contextually appropriate antiretroviral therapy (ART) programs for adolescent girls and young women (AGYW) aged 15-24 living with HIV in Dar es Salaam. In Tanzania, a quarter of all new annual HIV infections are among AGYW. Despite efforts to decrease incident infections, the number of AGYW living with HIV in southern and eastern Africa continues to rise and increasingly, the burden is among those with sexually acquired HIV . Further, more than half of the 130,000 AGYW living with HIV in Tanzania are virally unsuppressed, increasing their risk for onward HIV transmission, morbidity, and mortality. Few evidence- based interventions exist to improve retention in care and viral suppression for adolescents, and even fewer have been implemented at scale. Peer support models known as “teen clubs” have been prioritized by PEPFAR and the Government of Tanzania for scale up. Yet evidence to support the feasibility, acceptability, and effectiveness of this intervention is mixed, and implementation research is needed to close the evidence to practice gap. Guided by a community-driven implementation planning framework and the Consolidated Framework for Implementation Research (CFIR), we propose the following aims in Dar es Salaam: (1) Examine the social, structural, and clinic-level factors associated with retention in care and HIV viral suppression among AGYW participating in the DREAMS prevention program who were newly infected or diagnosed with HIV; (2) Refine a tailored package of implementation strategies to optimize a peer-support model for HIV treatment; and (3) Pilot the feasibility, acceptability, and preliminary effectiveness of a t...