PROJECT SUMMARY/ABSTRACT In the United States, HIV and sexually transmitted infections (STIs) disproportionately affect adolescents and young adults (AYA). Youth aged 13-24 years comprise ~21% of incident HIV cases. In addition, 2017 data demonstrated the fourth consecutive year of increasing STI rates, with the highest incidence occurring in AYA. Amidst these public health challenges, the 2018 licensure of tenofovir-emtricitabine as HIV pre-exposure prophylaxis (PrEP) for adolescents presents a key opportunity for enhancing youth HIV and STI prevention services. Currently, <2% of U.S. PrEP prescriptions are for adolescents <18 years of age. Pediatric primary care providers (PCPs) are thus well-positioned to expand PrEP delivery. However, sexual health service delivery in primary care is hampered by PCP time constraints and competing demands. There is a critical need for both behavioral interventions to increase PrEP uptake and reduce STIs in adolescents, and implementation strategies to disseminate PrEP and enhanced sexual health services in adolescent primary care. The goal of this K23 application is to facilitate Dr. Sarah M. Wood’s long-term goal of becoming an independent investigator in adolescent HIV and STI prevention through an integrated program of training and applied research that will prepare her to meet the challenges of the current HIV and STI epidemics. This award will also focus on her short-term goal of gaining the methodologic expertise needed to adapt, optimize for implementation, and test, a developmentally-tailored, PrEP-inclusive, HIV/STI prevention health coaching intervention for adolescents in primary care. The training objectives focus on content areas where she currently lacks the methodologic expertise to carry out this goal: 1) bio-behavioral intervention adaptation, 2) implementation science, and 3) clinical trial methodology. This training plan will be bolstered by a highly skilled mentorship team with expertise in intervention development, adolescent sexual health and qualitative methodology, and primary care pragmatic clinical trials. The advisory team will provide further expertise in developmental tailoring, prevention science, implementation science, mental health measurement and targets, and clinical trial design and analysis. Dr. Wood’s training objectives will progress in parallel with, and inform, her applied research aims. Aim 1 will use qualitative methods and the ADAPT-ITT framework to adapt the health coaching intervention. Aim 2 will determine acceptability and feasibility of the intervention among primary care providers, and develop an optimized primary care implementation strategy for the intervention. Finally, Aim 3 will conduct a smal...