It’s already a potent weapon against HIV, but Truvada, a combination of two antiviral medications, is now the first drug-based way to prevent infection against the virus among healthy people. After groundbreaking trials showed that uninfected individuals using the medication could lower their risk of acquiring HIV, the Food and Drug Administration expanded Truvada’s approval to include healthy people at high risk of becoming infected with HIV. Studies showed that high-risk gay men as well as the uninfected partner of an HIV-positive patient lowered their chances of becoming positive by anywhere from 42% to 75%. While critics are concerned that the treatment may lead to higher-risk behavior, like unprotected sex, public health experts welcome the new way of fighting AIDS: preventing infections from occurring in the first place.