Advancing pharmacy-based delivery of primary STI and HIV prevention for cisgender women - ABSTRACT Sexually transmitted infections (STIs) disproportionately affect cisgender adolescent girls and young women (AGYW) who often experience STI complications, including infertility, chronic pelvic pain, and increased risk for HIV acquisition and peripartum morbidity. Approximately one in four AGYW in East Africa have Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), or syphilis. In Kenya, HIV and STIs comprise a syndemic with 40% of new HIV infections occurring among AGYW. Yet, research to address STIs lags behind HIV in this priority population and no primary STI prevention tools are currently available to cisgender women beyond condoms. In Kenya, 40% of women access contraception without interfacing with facilities, including at retail pharmacies, and are missed by facility-based HIV services like pre-exposure prophylaxis (PrEP). In our ongoing work among AGYW seeking contraception at 20 pharmacies in Kisumu, Kenya (NCT05467306); all AGYW offered STI testing accepted, 29% had CT or NG, and 70% accepted expedited partner therapy (EPT) and report no social harms. Among AGYW seeking emergency contraception, only 3% previously used HIV post-exposure prophylaxis (PEP), highlighting an opportunity to offer HIV PEP to AGYW via pharmacies. These preliminary data support that strategies to address STIs and promote HIV PEP/PrEP use for AGYW would be ‘high-yield’ in pharmacies. Qualitative data suggest that STI testing motivates health promoting behaviors, even when STI results are negative. To date, no studies evaluate if serial STI testing promotes PrEP persistence. ‘Event-driven’ doxycycline PEP (doxy-PEP) for CT, NG, and syphilis found no protective benefit for Kenyan women accessing PrEP at facilities, likely due to low adherence. AGYW more frequently access emergency contraception at pharmacies compared to facilities; thus, ‘event-driven’ strategies, like HIV PEP (“PEP-in-Pocket”) or doxy-PEP, may have higher use in pharmacies. We propose a RCT in Kisumu, Kenya–a region with 20% HIV prevalence–to test co- offering HIV PEP/PrEP and STI testing with and without doxy-PEP in pharmacies and prospectively assess HIV PEP/PrEP use and persistence, and STI incidence among AGYW (n=720). Aim 1 will conduct a 3-arm RCT among AGYW seeking contraception at pharmacies to compare HIV PEP/PrEP delivery with: 1) serial STI testing and doxy-PEP vs. 2) serial STI testing alone vs. 3) no serial STI testing or doxy-PEP. Aim 2 will assess implementation outcomes to inform scale up of integrating HIV PEP/PrEP, STI testing, EPT, and doxy-PEP into pharmacies using operational data, interviews, and surveys. Aim 3 will estimate cost and cost-effectiveness by incorporating time-and-motion data and micro-costing. We hypothesize that expanding HIV and STI prevention options to include HIV PEP, STI testing, EPT, and doxy-PEP in pharmacies will be cost-effective and improve HIV and STI outcomes in AGYW, a population disproportionately affected by STIs and HIV. Our study is designed to inform pharmacy delivery of HIV PEP/PrEP, STI testing, EPT, and doxy-PEP and provide evidence to inform policy and WHO guidelines for STI/HIV prevention among AGYW.