Background: PROUD demonstrated an 86% reduction in HIV-acquisition among participants offered PrEP in the first year of follow-up, with high levels of adherence. Relatively little is known about long-term PrEP adherence. We report adherence intentions, long-term adherence and HIV-acquisition among PrEP users in PROUD.
Methods: We tabulated data from the ''end-of-study-questionnaire'' (EoS), which asked about adherence intentions. We calculated the medication possession ratio (MPR) as the number of pills prescribed, divided by number of days elapsed since PrEP initiation. We describe sero-conversions among participants who initiated PrEP.
Results: PROUD ran from Nov12 to Nov16, enrolled 544 participants and accumulated 1,253.3 person years of follow-up. Of 310 participants who completed the EoS, 86% aimed to use PrEP daily during the study, reducing to 61% wanting to use it daily after the trial. 98% thought their adherence was ''good enough'' during periods of risk. 36% reported intentionally interrupting/stopping PrEP. Of 481 participants who initiated PrEP, 327(68%) received a prescription within the last 6-months of the study. The MPR from PrEP initiation to end of first-year of use was high at 92%, reducing cumulatively to 82% and 76% from initiation to end of years 2 and 3. We observed 10 HIV infections among participants who initiated PrEP. One participant acquired HIV before baseline, four stopped attending clinic without providing a reason, two stopped attending clinic after reporting changing to on-demand dosing or stopping PrEP, and three attended clinic but did not collect PrEP(Figure 1).

Figure 1
[Figure 1]

Conclusions: In this study, which recommended daily-dosing, the majority of participants intended to use PrEP daily, over a third reported intentionally interrupting PrEP and a third stopped using PrEP within 4-years of initiation. When attending clinic, adherence was high but declined over time. The seroconversion data highlights the urgent need for interventions to help people know when to cycle on and off PrEP.