Sexually transmitted infections incidence in young Thai men who have sex with men and transgender women using HIV pre-exposure prophylaxis

Background Sexually transmitted infections are a major public health issue worldwide. HIV pre-exposure prophylaxis (PrEP) use among youth may be associated with increased incidence of sexually transmitted infections (STIs). Objectives To measure the prevalence and incidence of STIs among young men who have sex with men (YMSM) and young transgender women (YTGW) using PrEP. Methods A prospective cohort of 15- to 19-year-old YMSM and YTGW with HIV risk defined as inconsistent condom use and/or multiple sex partners were enrolled. Participants were provided daily oral tenofovir disoproxil fumarate/emtricitabine. STI screening was done at baseline and month 6 for syphilis, urine, and anal swab nucleic acid amplification testing for C. trachomatis (CT) and N. gonorrheaoe (NG). Results From March 2018 to June 2019, 200 adolescents (147 MSM and 53 TGW) with a median (IQR) age of 18 years (17-19) were enrolled. STI prevalence was 22.5% (95% CI 16.7-28.3). STI incidence was 25.2 per 100 person-years (95% CI 14.7, 40.3). Factors associated with STI incidence were self-reported >2 sex partners in the past month (unadjusted rate ratio [uRR] 4.6, 95% CI 1.0, 20.6), and moderate PrEP adherence (uRR 7.3, 95% CI 1.6, 32.6). Conclusions STI incidence in YMSM and YTGW PrEP users was high at approximately one in five. Regular screening and treatment of STIs should be implemented in youth HIV prevention packages.