Daily oral pre-exposure prophylaxis (PrEP) against HIV works as well in women with abnormal vaginal microbiota as in women with normal levels of vaginal flora. This new finding addresses concerns arising from previous research that suggested that an anti-HIV vaginal gel might not effectively prevent the virus among women with bacterial vaginosis or other indicators of an imbalance in the vaginal microbiome.

Researchers for the study analyzed data from the placebo-controlled Phase III Partners PrEP Study, which gave women Truvada (tenofovir disoproxil fumarate/emtricitabine), Viread (tenofovir disoproxil fumarate) or a placebo with instructions to take the tablets daily. The women were highly adherent to the medication, and PrEP ultimately had a greater than 70 percent overall efficacy among them.

Renee Heffron, PhD, MPH, of the University of Washington presented findings from the study at the 2017 Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle.

The investigators conducted a substudy of 1,470 women whose bacterial vaginosis status was measured annually. Sixty-seven percent of them were randomized to PrEP.  Their median age was 33. Twenty-four percent had bacterial vaginosis when they entered the trial, while 12 percent had intermediate microbiota and 64 percent had normal microbiota.

PrEP’s efficacy was 73 percent among those with normal microbiota, 63 percent among those with intermediate microbiota and 77 percent among those with bacterial vaginosis. The differences between these rates were not statistically significant different, meaning they may have been driven by chance.

There was also no statistical difference in PrEP efficacy based on the detection of certain indicators of abnormal vaginal microbiota. The respective efficacy associated with detected versus undetected Gardnerella/Bacteroides was 69 percent and 77 percent; with Lactobacillus crispatus, the respective corresponding figures were 74 percent and 70 percent.

The researchers concluded that there was no indication that abnormal vaginal microbiomes affected the efficacy of PrEP.

“PrEP works in women when it is taken, including among those with abnormal microbiota,” Heffron told CROI attendees. “These data are reassuring that the delivery of oral PrEP to women does not need to be contingent upon testing for [bacterial vaginosis].”