PrEP surfing: HIV pre-exposure prophylaxis (PrEP) 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 pre-exposure prophylaxis (PrEP) use of one's sex partner is referred to as PrEP surfing. We aimed to estimate the proportion of 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 behaviour, 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 2,187 visits from 636 participants to analyse intention for PrEP surfing. Median age was 45 (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, 1,779 visits from 562/636 (88%) participants with event-driven/no PrEP use were analysed. Recent PrEP surfing was reported in 449/1,779 (25%) visits. Median intention for PrEP surfing was 4 (IQR = 1-6); in 588/2,187 (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.