Missed opportunities to prevent HIV infections among pre-exposure prophylaxis users: a population-based mixed methods study, San Francisco, United States.

INTRODUCTION: Pre-exposure prophylaxis (PrEP) is highly effective, although PrEP adherence and persistence has been variable during real world implementation. Little is known about missed opportunities to enhance PrEP adherence among individuals who later HIV seroconverted after using PrEP. The goal of this analysis was to identify all HIV infections among individuals who had accessed PrEP in an integrated health system in San Francisco, and to identify potentially intervenable factors that could have prevented HIV infection through in-depth interviews with people who HIV seroconverted after using PrEP. METHODS: We identified individuals who initiated PrEP in an integrated safety-net public health system and performed in-depth chart review to determine person-time on and after stopping PrEP over six years. We identified all PrEP seroconversions using the Centers for Disease Control and Prevention's Enhanced HIV/AIDS Reporting System and then calculated HIV incidence while using PrEP and during gaps in use. We then performed in-depth interviews with those who seroconverted. RESULTS: Overall, 986 initiated PrEP across the San Francisco Department of Public Health from July 2012 to November 2018. Data were gathered from 895 person-years on PrEP and 953 after stopping PrEP. The HIV incidence was 7.5-fold higher after stopping PrEP compared to while on PrEP (95% CI 1 to 336). Of the eight individuals who HIV seroconverted; only one was taking PrEP at the time of seroconversion but was using on-demand PrEP inconsistently. All eight agreed to qualitative interviews. Major barriers to PrEP persistence included substance use, mental health and housing loss; difficulty accessing PrEP due to cost, insurance, and the cost and time of medical visits; difficulty weighing PrEP's benefit versus self-perceived risk; and entering a primary partnership. The individual who developed HIV using on-demand PrEP reported confusion about the dosing regimen and which sexual encounters required accompanying PrEP dosing. CONCLUSIONS: HIV incidence during gaps in PrEP use was nearly eight-fold higher than while on PrEP in this large cohort in San Francisco. Many individuals who stop PrEP remain at risk of HIV, and participants reported that proactive outreach could potentially have prevented HIV infections. Individuals using non-daily PrEP may require additional education and support in the United States.

Quarterly screening optimizes detection of sexually transmitted infections when prescribing HIV preexposure prophylaxis.

OBJECTIVE: The optimal screening frequency of sexually transmitted infections (STIs) for MSM and transgender women (TGW) on HIV pre-exposure prophylaxis (PrEP) is unclear, with present guidelines recommending screening every 3-6 months. We aimed to determine the number of STIs for which treatment would have been delayed without quarterly screening. DESIGN: The US PrEP Demonstration Project was a prospective, open-label cohort study that evaluated PrEP delivery in STI clinics in San Francisco and Miami, and a community health center in Washington, DC. In all, 557 HIV-uninfected MSM and TGW were offered up to 48 weeks of PrEP and screened quarterly for STIs. METHODS: The proportion of gonorrhea, chlamydia, and syphilis infections for which treatment would have been delayed had screening been conducted every 6 versus every 3 months was determined by taking the number of asymptomatic STIs at weeks 12 and 36 divided by the total number of infections during the study follow-up period for each STI. RESULTS: Among the participants, 50.9% had an STI during follow-up. If screening had been conducted only semiannually or based on symptoms, identification of 34.3% of gonorrhea, 40.0% of chlamydia, and 20.4% of syphilis infections would have been delayed by up to 3 months. The vast majority of participants (89.2%) with asymptomatic STIs reported condomless anal sex and had a mean of 8.1 partners between quarterly visits. CONCLUSIONS: Quarterly STI screening among MSM on PrEP could prevent a substantial number of partners from being exposed to asymptomatic STIs, and decrease transmission.