Carlos del Rio, MD

In a substudy of the Partners PreP trial, efficacy was 100% with closely monitored adherence and stepped-up counseling if levels fell below 80%.

Efficacy of pre-exposure prophylaxis (PrEP) in recent trials has ranged from zero to 75%, with the differences explained in large part by disparities in adherence among the studies. In a substudy cohort within the Partners PreP Study (a randomized, placebo-controlled trial of daily oral PrEP among HIV-uninfected members of serodiscordant couples in Kenya and Uganda), investigators optimized study-medication adherence through close surveillance — unannounced home-based pill counts and electronic pill-bottle monitoring — and provided intensive counseling if adherence fell below 80%.

The substudy involved 1147 HIV-seronegative participants (53% men; median age, 34) enrolled from three study sites in Uganda. Ninety-nine percent of them were married (median duration of partnership, 8.5 years), and 29% reported unprotected sex during the preceding month. Fourteen HIV infections occurred, all in the placebo arm, for a PrEP efficacy of 100% (95% confidence interval, 83.7%–100%). Overall adherence was high (median, 99.1% by pill count and 97.2% by electronic monitoring). Factors independently associated with <80% adherence by pill count were report of no sexual activity, sex with both the study partner and another partner during the preceding month, younger age, and heavy alcohol use; being in a “formal” polygamous relationship was associated with a lower likelihood of <80% adherence. Similar findings (except for alcohol use) were seen for <80% adherence by electronic monitoring.

Citation(s):

Haberer JE et al. Adherence to antiretroviral prophylaxis for HIV prevention: A substudy cohort within a clinical trial of serodiscordant couples in East Africa. PLoS Med 2013 Sep: e1001511.