When preventing HIV, bacteria in the vagina matter

Some microbes appear to break down drug in prophylactic gel, making it less effective

applicator

DOSE OF GEL  Women use an applicator (shown) to self-administer a vaginal gel containing the HIV-prevention drug tenofovir. Vaginal bacteria affect how well the drug works, a new study suggests.

CAPRISA

Bacteria in the vagina affect whether a drug stops an HIV infection or is itself stopped cold.