PURPOSE OF REVIEW:
The review describes the current understanding of adherence to oral preexposure prophylaxis (PrEP), methods for adherence measurement, approaches to supporting PrEP adherence, and guidance for defining PrEP adherence goals within the larger context of HIV prevention.
PrEP adherence has generally been higher in recent trials, open-label extensions, and demonstration projects compared with the initial clinical trials; potential explanations include known PrEP efficacy and different motivations to take PrEP. Recent studies have explored adherence monitoring through electronic pill containers, short message service (SMS), and drug concentrations in hair and dried blood spots. The few PrEP adherence interventions developed to date include combinations of enhanced counseling, feedback of objective adherence measurement, and SMS. Conceptualization of PrEP adherence is evolving. The goal is not 100% adherence indefinitely, as it was in clinical trials. PrEP adherence should be defined with respect to HIV exposure, which varies over time by sexual behavior and use of other prevention strategies.
PrEP adherence beyond clinical trials has generally been high enough to achieve reliable HIV prevention. Future efforts to measure and support PrEP adherence should focus on the context of risk for HIV acquisition, accounting for dynamic behaviors and choices among HIV prevention options.