WASHINGTON — The Food and Drug Administration on Monday approved the first drug shown to reduce the risk of HIV infection, the latest milestone in the 30-year battle against the virus that causes AIDS.

The agency approved Gilead Sciences‘ pill Truvada as a preventive measure for healthy people who are at high risk of acquiring HIV through sexual activity, such as those who have HIV-infected partners. The decision comes less than two weeks after the agency approved another landmark product: the first over-the-counter HIV test that can be developed at home.

The two developments are seen as the biggest steps in years toward curbing the spread of HIV in the U.S., which has held steady at about 50,000 new infections per year for the last 15 years. An estimated 1.2 million Americans have HIV, which develops into AIDS unless treated with antiviral drugs. And an estimated 240,000 HIV carriers are unaware that they are infected.