Daily oral tenofovir-based PrEP demonstrated high efficacy in clinical trials for HIV prevention among women with high adherence. Recent data suggest that vaginal tenofovir gel may not effectively prevent HIV among women with bacterial vaginosis or other indicators of vaginal dysbiosis (e.g., non-Lactobacillus or Gardnerella¬ predominance). Those data raised concern whether daily oral tenofovir could be less effective among women with abnormal vaginal microbiota.
Using data from women in the Partners PrEP Study, a phase III placebo-controlled trial of daily oral PrEP conducted in Kenya and Uganda that had high (~80%) PrEP adherence and overall efficacy >70% in women, we assessed PrEP efficacy among subgroups of women defined by bacterial vaginosis status, measured annually. Nugent score by microscopy was used to measure bacterial vaginosis, with 0-3 indicating normal, 4-6 intermediate, and 7-10 bacterial vaginosis. We also considered the separate components of the Nugent score: detection of Gardnerella/Bacteroides and non-detection of Lactobacillus as markers of abnormal vaginal microbiota.
Of 1470 women, the median age was 33 years (13% were aged <25 years), and 24% had bacterial vaginosis at enrollment. PrEP had comparable efficacy for HIV prevention among women with normal microbiota (efficacy=77%), intermediate microbiota (73%), and bacterial vaginosis (63%) (interaction p-value=0.9, Figure). Similarly, PrEP efficacy was not different among women with detected versus undetected Gardnerella/Bacteroides (69% efficacy versus 77%, interaction p=0.7) and Lactobacillus (74% versus 70%, interaction p=0.9).
Among African women with a high prevalence of bacterial vaginosis and high PrEP adherence, the efficacy of daily oral PrEP was not different among women with abnormal versus normal vaginal microbiota. Bacterial vaginosis and other indicators of vaginal dysbiosis do not diminish the efficacy of oral PrEP for HIV prevention.