PrEP surfing: HIV preexposure prophylaxis use of sex partners as HIV prevention strategy among men who have sex with men

OBJECTIVE: Having condomless anal sex while relying on the HIV preexposure prophylaxis (PrEP) use of one's sex partner is referred to as PrEP surfing. We aimed to estimate the proportion of men who have sex with men (MSM) practicing PrEP surfing, their intention to practice it, and determinants of both. DESIGN: Open prospective cohort study. METHODS: We included MSM participating in the Amsterdam Cohort Studies in 2021-2023. Biannually, participants completed questionnaires on recent (=preceding 6 months) sexual behavior, including PrEP use, PrEP surfing, and intention for both in the coming 6 months (7-point Likert scale). We assessed determinants of PrEP surfing with logistic regression and determinants of intention with linear regression. RESULTS: We included 2187 visits from 636 participants to analyze intention for PrEP surfing. Median age was 45 [interquartile range (IQR) = 34-52] years, median number of recent sex partners 4 (IQR = 1-11), and 264 (41%) participants reported recent PrEP use. For recent PrEP surfing, 1779 visits from 562/636 (88%) participants with event-driven/no PrEP use were analyzed. Recent PrEP surfing was reported in 449/1779 (25%) visits. Median intention for PrEP surfing was 4 (IQR = 1-6); in 588/2187 (27%) visits, intention for PrEP surfing was high (=score 6-7). Recent PrEP use and high perceived probability of acquiring HIV were associated with recent PrEP surfing and higher intention, while age ≥45 and having a steady partner were inversely associated. Having ≥3 recent partners was associated with recent PrEP surfing. CONCLUSIONS: PrEP surfing is a common HIV prevention strategy among MSM in Amsterdam. Its effectiveness needs to be determined to optimize HIV prevention care.