Alignment of adherence and risk for HIV acquisition in a demonstration project of pre‐exposure prophylaxis among HIV serodiscordant couples in Kenya and Uganda: a prospective analysis of prevention‐effective adherence

Introduction: Adherence is essential for pre‐exposure prophylaxis (PrEP) to protect against HIV acquisition, but PrEP use need not be life‐long. PrEP is most efficient when its use is aligned with periods of risk – a concept termed prevention‐effective adherence. The objective of this paper is to describe prevention‐effective adherence and predictors of adherence within an open‐label delivery project of integrated PrEP and antiretroviral therapy (ART) among HIV serodiscordant couples in Kenya and Uganda (the Partners Demonstration Project). Methods : We offered PrEP to HIV‐uninfected participants until the partner living with HIV had taken ART for ≥6 months (a strategy known as “PrEP as a bridge to ART”). The level of adherence sufficient to protect against HIV was estimated in two ways: ≥4 and ≥6 doses/week (per electronic monitoring). Risk for HIV acquisition was considered high if the couple reported sex with <100% condom use before six months of ART, low if they reported sex but had 100% condom use and/or six months of ART and very low if no sex was reported. We assessed prevention‐effective adherence by cross‐tabulating PrEP use with HIV risk and used multivariable regression models to assess predictors of ≥4 and ≥6 doses/week. Results : A total of 985 HIV‐uninfected participants initiated PrEP; 67% were male, median age was twenty‐nine years, and 67% reported condomless sex in the month before enrolment. An average of ≥4 doses and ≥6 doses/week were taken in 81% and 67% of participant‐visits, respectively. Adherence sufficient to protect against HIV acquisition was achieved in 75–88% of participant‐visits with high HIV risk. The strongest predictor of achieving sufficient adherence was reporting sex with the study partner who was living with HIV; other statistically significant predictors included no concerns about daily PrEP, pregnancy or pregnancy intention, females aged > 25 years, older male partners and desire for relationship success. Predictors of not achieving sufficient adherence were no longer being a couple, delayed PrEP initiation, >6 months  of follow‐up, ART use > 6 months  by the partner living with HIV and problem alcohol use. Conclusions: Over three‐quarters of participant‐visits by HIV‐uninfected partners in serodiscordant couples achieved prevention‐effective adherence with PrEP. Greater adherence was observed during months with HIV risk and the strongest predictor of achieving sufficient adherence was sexual activity.