South African Adolescent Girls and Young Women (AGYW), ages 15 – 19 years-old, are at high risk of new sexually transmitted infections, including HIV. Ongoing efforts to stem transmissions have been disappointing. Family-based prevention programs are an underutilized approach in the HIV prevention toolkit, despite evidence of their promise in improving AGYW health prevention attitudes and behaviors. This one-year diversity supplement will support Alyssa Debra's career development as a physician scientist who is beginning her PhD after completing two years of medical school. Her research study builds on the parent grant, a 2-arm randomized controlled trial testing a female caregiver (FC)-daughter HIV/STI prevention program on South African AGYW STI and HIV incidence. Using UG3 pilot data from the parent study, Alyssa will evaluate two theoretical mechanisms believed to explain change in AGYW STI and HIV outcomes: FC-AGYW relationships and communication, and AGYW HIV/STI knowledge, attitudes, and skills. Alyssa will examine change in these mechanisms from baseline to 6-month follow-up (after the intervention), and she will compare changes in the experimental and control arms. Findings will set the stage to evaluate the role of these mechanisms on the primary and secondary outcomes of the parent project. The career development plan specifies a combination of hands-on experiential training, coursework, guided readings, one-on-one meetings with mentors, and networking opportunities to achieve Alyssa's three training goals: (1) global health research, (2) implementation science, and (3) adolescent health disparities. Alyssa has assembled an expert mentorship team who will facilitate her engagement in research and training activities. Each month, she will review her progress with Dr. Donenberg to ensure she is on track to meet her deliverables. Taken together, the combination of experiences, close mentorship, and oversight by Dr. Donenberg, Alyssa will receive a strong foundation to prepare her for a future research career.