Sexual relationships outside primary partnerships and abstinence are associated with lower adherence and adherence gaps: Data from the partners PrEP ancillary adherence study

Objective: To assess the role of sexual relationships on levels and patterns of adherence to medication for pre-exposure prophylaxis against HIV. Methods: We enrolled 1147 HIV-negative individuals in long-term serodiscordant relationships at 3 sites in Uganda from the Partners Pre-exposure Prophylaxis Study, a randomized placebo-controlled trial of daily oral tenofovir and emtricitabine/tenofovir. We used generalized estimation equations to assess the effects of sexual relationships on low adherence (<80%) and on gaps in adherence. Results: Fifty-three percent were male, 51% were 18-34 years and 24% were polygamous. Participants who reported sex in the past month with someone other than their primary partner and with <100% condom use were more than twice as likely to have low adherence [adjusted odds ratio (aOR) = 2.48, 95% CI: 1.70 to 3.62] compared with those who had sex with only their primary partners and 100% condom use. Using the same reference group, those who abstained from sex in the previous month had 30% increased odds of low adherence (aOR = 1.30, 95% CI: 1.05 to 1.62) and participants in nonpolygamous marriages who reported sex with both their primary and other partners and <100% condom use were almost twice as likely to be low adherers (aOR = 1.76, 95% CI: 1.01 to 3.08). At least one 72-hour gap in adherence was seen in 598 participants (54.7%); 23.2% had at least one 1-week gap. Conclusions: Risk of low overall adherence was higher in participants who reported sex outside primary partnerships and suboptimal condom use, as well as in those who abstained from sex. Adherence gaps were common, potentially creating risk for HIV acquisition.