Correlates of Adherence to Oral and Vaginal Pre-exposure Prophylaxis (PrEP) Among Adolescent Girls and Young Women (AGYW) Participating in the MTN-034/REACH Trial

We evaluated correlates of adherence to PrEP, including daily oral tenofovir disoproxil fumarate in combination emtricitabine (oral FTC/TDF) and the monthly dapivirine ring (ring)among adolescent girls and young women (AGYW) in the MTN-034/REACH study. We enrolled 247 AGYW aged 16-21 years in South Africa, Uganda and Zimbabwe (ClinicalTrials.gov: NCT03074786). Participants were randomized to the order of oral FTC/TDF or ring use for 6 months each in a crossover period, followed by a 6-month choice period. We assessed potential adherence correlates-individual, interpersonal, community, study, and product-related factors-quarterly via self-report. We measured biomarkers of adherence monthly; high adherence was defined as > 4 mg dapivirine released from returned rings or intracellular tenofovir diphosphate levels ≥ 700 fmol/punch from dried blood spots (DBS). We tested associations between correlates and objective measures of high adherence using generalized estimating equations. High adherence to oral FTC/TDF was significantly associated with having an older primary partner (p = 0.04), not having exchanged sex in the past 3 months (p = 0.02), and rating oral FTC/TDF as highly acceptable (p = 0.003). High ring adherence was significantly associated with unstable housing (p = 0.01), disclosing ring use to a male family member (p = 0.01), and noting a social benefit from study participation (p = 0.03). All associations were moderate, corresponding to about 6%-10% difference in the proportion with high adherence. In our multinational study, correlates of adherence among African AGYW differed for oral FTC/TDF and the ring, highlighting the benefit of offering multiple PrEP options.