Abstract
BACKGROUND: In recent years there has been an increase in the diagnoses of sexually transmitted infections (STI) among men who have sex with men (MSM) using human immunodeficiency virus (HIV) pre-exposure prophylaxis (PrEP); however, data on PrEP users in Austria are limited. PATIENTS, MATERIAL AND METHODS: In June 2020, we initiated a prospective observational cohort study at Vienna General Hospital including PrEP users from Vienna. Participants underwent STI testing quarterly and provided behavioral information using a questionnaire. RESULTS: Between June 2020 and December 2023 a total of 360 individuals (99% MSM) were enrolled comprising 379 person-years of follow-up. We identified 276 STIs in 154 individuals, of which 23% (36/154) were symptomatic. The incidence rates per 100 person-years were 29.9 (95% confidence interval, CI 24.3-35.3 per 100 person-years) for gonorrhea, 22.7 (95% CI 17.9-27.5 per 100 person-years) for chlamydia and 9.8 (95% CI 6.6-12.9 per 100 person-years) for syphilis. Extragenital infections accounted for 95% (97/102) of gonorrhea and 81% (65/80) of chlamydia cases. A case of HIV infection was recorded in a 20-year-old male with inconsistent PrEP use. Participants with one or more reinfection (18%; 65/360) accounted for 68% (187/276) of all STIs. Sexualized drug use (Chemsex) was reported by 44% (157/360) of participants and was significantly associated with higher rates of gonorrhea (38% vs. 21%, p < 0.001) and syphilis (17% vs. 5%, p < 0.001) but not chlamydia (26% vs. 19%, p = 0.118). CONCLUSION: Throughout the study, 43% of participants experienced a bacterial STI, which was mostly asymptomatic and at extragenital sites. Chemsex was commonly reported and identified as a predictor for STI reinfection, underlining the importance of harm reduction strategies in Austrian STI prevention.