Background: There has been mixed evidence about the extent to which gay and bisexual men (GBM) who use PrEP engage in greater condomless anal sex (CAS) and acquire STIs more frequently. Many studies rely on between-group comparisons of PrEP users and non-users or lack longitudinal data before and after PrEP initiation. The current study sought to examine within-person changes among men who electively initiated?and in some cases, discontinued?PrEP while enrolled in an observational study.
Methods: Data were taken from a longitudinal study of 1,071 HIV-negative GBM from across the U.S. Participants were tested annually for rectal gonorrhea and chlamydia and reported on PrEP use and CAS. We examined the odds of diagnosis with a rectal STI, number of CAS acts with casual male partners, and receptive CAS acts with serodiscordant casual male partners by PrEP status using general estimating equations; models were adjusted for visit year, relationship status, and race.
Results: We analyzed all data from the 281 (26.2%) GBM reporting PrEP use at one or more visits?1012 person-visits of data were examined, of which 517 (51.1%) were prior to initiation, 406 (40.1%) were while on PrEP, and 89 (8.8%) were after discontinuation. Overall prevalence of rectal STIs was 8.6%, with no significant changes in the odds while on PrEP (AOR = 1.28, p = 0.36) or after discontinuing (AOR = 0.28, p = 0.08) compared to pre-uptake. There were significant increases in CAS with casual male partners (AOR = 2.49, p < 0.001) and receptive CAS with serodiscordant male partners (AOR = 8.02, p < 0.001) while on PrEP compared to before uptake; no significant differences were observed in CAS comparing pre-PrEP and post-PrEP assessments.
Conclusions: Despite substantial within-person increases in CAS, including receptive CAS with serodiscordant partners, we failed to observe statistically significant increases in rectal STI incidence. It is likely that the desire for CAS was a motivator for initiating PrEP and GBM feel more comfortable having CAS while on PrEP. At discontinuation, however, CAS returned to pre-PrEP use levels, suggesting GBM are quite capable of other HIV prevention strategies when no longer on PrEP.