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 …