Use of non-occupational post-exposure prophylaxis does not lead to an increase in high risk sex behaviors in men who have sex with men participating in the EXPLORE trial.

Non-occupational post-exposure prophylaxis (nPEP) use is an HIV prevention strategy that has been recommended by the CDC to prevent HIV infection after a high risk sexual exposure since 1997. In a behavioral intervention trial of 4,295 MSM we assessed perceptions and use of nPEP over 4 years in six cities across the United States. Overall, 1.9% of MSM reported use of nPEP prior to enrollment, and 6.3% at least once during the trial. Awareness of nPEP was reported by 47.5%, with higher awareness in two sites with funded nPEP programs. Three seroconversions occurred in the 384 visits where nPEP courses were reported, with no effect of nPEP on risk of HIV acquisition in this cohort (hazard ratio = 0.91, 95% confidence interval [0.29, 2.86]). NPEP users were a riskier group: increased odds of nPEP use were observed in association with multiple partners and unprotected receptive and insertive anal sex with HIV infected partners and partners with unknown HIV status. NPEP use was also associated with use of illicit drugs (injection drugs, crack cocaine, hallucinogens, and amphetamines). Importantly, willingness to use nPEP after high risk sex was associated with lower odds of high risk sex. After an episode of nPEP use, nPEP users remained more likely to report high risk sex than those in this cohort who had not previously used nPEP. However, within the subset of people who had previously reported high risk sex, previous nPEP use was not associated with higher odds of high risk sex, thus allaying fears that availability of nPEP would lead to an increase in high risk sex.