[Sexual behaviour and incidence of sexually transmitted infections among men who have sex with men (MSM) using daily and event-driven pre-exposure prophylaxis (PrEP): Four-year follow-up of the Amsterdam PrEP (AMPrEP) demonstration project cohort].

OBJECTIVE

HIV can be effectively prevented by oral HIV pre-exposure prophylaxis (PrEP). When PrEP was introduced, there was apprehension that condom use would decrease and STIs would increase. The purpose of this study was to investigate sexual behaviour and STI incidence among PrEP users.

DESIGN

Prospective cohort study METHODS: The Amsterdam PrEP demonstration project (AMPrEP) provided oral PrEP to men who have sex with men (MSM) and transgender women from 2015 to 2020. Participants could choose between daily and event-driven PrEP. We tested for HIV and STIs at each quarterly study visit. We examined changes in numbers of sex partners and frequency of condomless anal sex with casual partners (CAS) with negative binomial regression. We examined HIV incidence, and changes in STI incidence using Poisson regression.

RESULTS

367 participants (365 MSM) initiated PrEP, median duration of participation was 3.9 years (interquartile range[IQR]=3.4-4.0). Median number of sex partners per three months was 13 (IQR=6-26) and decreased with each additional year on PrEP (adjusted rate ratio[aRR]=0.86/year, 95%confidence interval[CI]=0.83-0.88). Frequency of CAS per three months was 10 (IQR=3-20.5) and also decreased (aRR=0.92/year, 95%CI=0.88-0.97). Incidence of any STI was 87/100PY (95%CI=82-92) and did not increase over time. Two HIV infections were diagnosed (incidence=0.2/100PY; 95%CI=0.0-0.6), both during the first year and among daily PrEP users.

CONCLUSIONS

In this prospective cohort with an observation period of four years, we observed a low HIV incidence and a decrease in the number of sex partners and CAS over time. Although STI incidence was high, it did not increase.