Untangling Hormonal Impacts on the Vaginal Microbiome and HIV Acquisition Risk

Mucosal microbiomes across the body influence susceptibility to disease and response to treatment. There is strong evidence that vaginal dysbiosis increases risk for HIV acquisition. Specifically, an acidic, healthy, lactobacilli-dominant vaginal environment decreases risk of HIV and other sexually transmitted infections (STIs), whereas a dysbiotic one increases HIV and STI risk. The relationship between hormonal contraception and HIV susceptibility is less clear. Studies of multiple contraception methods have found that hormonal contraception optimizes vaginal bacteria over time (as measured by decreased Nugent score). Dr. Achilles argued that these findings rule out dysbiosis as a pathway for hormonal contraception to increase HIV risk. Two possible mechanisms for an increase in HIV risk following initiation of hormonal contraception are changes in bleeding patterns and decreased condom use after starting hormonal contraception.

For the vaginal ring (NuvaRing), three months of available data demonstrated a decrease in dysbiosis, though accumulation of biomass on the ring was positively associated with dysbiosis. Considering these findings, Dr. Achilles identified several additional priority research questions: What happens to the vaginal microbiome when women have more bleeding, even if it is light spotting (as occurs in some women after starting hormonal contraception)? What happens to microbiome with vaginally delivered drugs? What are the longitudinal impacts of intrauterine devices (IUD) or implants on the vaginal microbiome, and how does the microbiome alter the metabolism and efficacy of these devices?