PrEP Use and Sexually Transmitted Infections Are Not Associated Longitudinally in a Cohort Study of Young Men Who Have Sex with Men and Transgender Women in Chicago.

Our goal was to understand whether PrEP users are at increased risk for STIs, a key target in prevention efforts aimed at disrupting the spread of STIs and likely downstream HIV infection risk. Data were collected as part of RADAR, a cohort study of young men who have sex with men and transgender women (YMSM/TW) (aged 16-29) in Chicago. Longitudinal lagged regression models were utilized to assess the relationship between PrEP use and odds of rectal STI acquisition. Mediation models were also utilized to consider the potential pathway between PrEP use, condomless anal sex (CAS), and rectal STI. One hundred eighty-seven (16.2%) participants had a rectal STI at baseline. In both cross-sectional and longitudinal models, no significant association was observed between PrEP use and STI. In mediation models, PrEP use was significantly associated with increased CAS, however, CAS was not associated with STI status. We demonstrated that, overall, PrEP use was not associated with STIs among YMSM/TW but did observe that PrEP users were more likely to report increased participation in CAS at the subsequent study visit.