Association of HIV preexposure prophylaxis with incidence of sexually transmitted infections among individuals at high risk of HIV infection

Abstract

IMPORTANCE, Emerging evidence suggests that risk of bacterial sexually transmitted infections, STIs, increases among gay and bisexual men following initiation of HIV preexposure prophylaxis, PrEP, . OBJECTIVE, To describe STI incidence and behavioral risk factors among a cohort of predominantly gay and bisexual men who use PrEP, and to explore changes in STI incidence following PrEP commencement. DESIGN, SETTING, AND PARTICIPANTS, The Pre-exposure Prophylaxis Expanded, PrEPX, Study, a multisite, open-label intervention study, was nested within the Australian Collaboration for Coordinated Enhanced Sentinel Surveillance, ACCESS, clinic network. A total of, participants were enrolled, July, April, in Victoria, Australia. Of these, enrolled at, ACCESS clinics, primary care, sexual health, and, community-based HIV rapid testing service, had at least, follow-up visit, and were monitored until April, . EXPOSURES, Upon enrollment, participants received daily oral tenofovir disoproxil fumurate and emtricitabine for HIV PrEP, quarterly HIV and STI testing, and clinical monitoring. MAIN OUTCOMES AND MEASURES, The primary outcomewas incidence of chlamydia, gonorrhea, or syphilis. Incidence rates and hazard ratios describing behavioral risk factors of STI diagnosis were calculated. Incidence rate ratios, IRRs, adjusted for change in testing frequency, described changes in STI incidence from, -year preenrollment to study follow-up among participants with preenrollment testing data, n, . RESULTS, Among the, individuals, median age, years, interquartile range, -, ., identified as gay or bisexual males, used PrEP prior to enrollment, withdrew andwere censored at date of withdrawal, leaving, ., enrolled at final follow-up. During a mean follow-up of, ., years, ., person-years, STIswere diagnosed among, participants, chlamydia, gonorrhea, syphilis, . STI incidencewas, ., per, person-years, with, participants, accounting for, of all STIs. Among, participants with complete data for multivariable analysis, younger age, greater partner number, and group sexwere associated with greater STI risk, but condom usewas not. Among, participants with preenrollment testing data, STI incidence increased from, ., per, person-years prior to enrollment to, ., per, person-years during follow-up, IRR, ., CI, ., -, ., . After adjusting for testing frequency, the increase in incidence from, year preenrollment to follow-upwas significant for any STI, adjusted IRR, ., CI, ., -, ., and for chlamydia, adjusted IRR, ., CI, ., -, ., . CONCLUSIONS AND RELEVANCE, Among gay and bisexual men using PrEP, STIs were highly concentrated among a subset, and receipt of PrEP after study enrollment was associated with an increased incidence of STIs compared with preenrollment. These findings highlight the importance of frequent STI testing among gay and bisexual men using PrEP.