Does bacterial vaginosis reduce PrEP's efficacy?

PrEP pill

Credit: NIAID (CC BY 2.0)

Previous research has shown that, for women with male partners, bacterial vaginosis (BV) can increase their risk of both acquiring and transmitting HIV. As a result, researchers have also hypothesized that BV could reduce the efficacy of PrEP, a drug-based HIV prevention strategy. A new Lancet HIV study coauthored by Dr. Craig Cohen is the first to evaluate that hypothesis among women taking PrEP orally.

The study found, “No evidence that the protective benefit of daily oral PrEP was reduced” in women with BV or otherwise unhealthy vaginal bacteria. In contrast, some studies focused on topically applied PrEP have found that BV does reduce its efficacy. One reason for the difference may be that topical PrEP methods, such as gels, are absorbed through local vaginal tissues and surfaces, which BV directly affects, whereas oral PrEP is distributed systemically.

One important caveat of this Lancet HIV study is that daily PrEP adherence was unusually high among all participants, including those with BV. Further research is needed to understand the relationship between PrEP’s efficacy and vaginal health among less adherent women. In the meantime, highly adherent women can be confident in PrEP’s efficacy, regardless of vaginal health.

Read more about a UCSF study developing innovative ways to treat BV.