Alignment of PrEP use and sexual behavior over four months among men who have sex with men in the southern United States.

Unlike antiretrovirals for HIV treatment, pre-exposure prophylaxis (PrEP) does not require continual adherence to be fully effective; rather, PrEP adherence is important only in the context of episodes of sexual risk. Therefore, studies of PrEP adherence and persistence must incorporate contemporaneous measurement of sexual behavior. Short, frequent surveys of PrEP use and sexual behavior allow for the measurement of the alignment between PrEP use and sexual behavior. We assessed the feasibility of using biweekly PrEP use and sexual behavior questionnaires to measure adherence and persistence on PrEP over a period of four months. We also measured the alignment of PrEP use and condomless anal sex. PrEP-using MSM in the southern US were recruited using online advertisements. Participants completed a baseline survey followed by brief surveys every two weeks for 16 weeks to report their PrEP use and sexual behavior over the preceding two-week period. Study retention was high: 91% of participants completed the baseline and final survey and, overall, 86% of study surveys were completed. Self-reported PrEP adherence and persistence were high, but instances of PrEP non-adherence were observed to frequently overlap with episodes of condomless anal sex. The most prominent reasons cited for missing PrEP doses were being too busy, not having PrEP on hand, and not being sexually active. Completing short, biweekly surveys of PrEP use and sexual behavior is feasible and acceptable to MSM in the southern US. Future studies should investigate incorporating biomarker measurements to validate self-reported adherence.