Two separate studies released Wednesday have found that taking a daily pill containing AIDS drugs can help keep an uninfected person from catching the virus. “This is an extremely exciting day for HIV prevention,” said Dr. Kevin Fenton, director of AIDS prevention at the Centers for Disease Control and Prevention in Atlanta. One of the studies, known as Partners PrEP, was conducted in Kenya and Uganda and found that participants who took a daily Truvada pill—a mix of tenofovir and emtricitabine—had a 73 percent lower chance of getting infected. Those who took a Viread pill, which contains only tenofovir, had a 62 percent lower chance. The second study, conducted in Botswana, found that those taking Truvada had a 63 percent lower chance of infection. These were the first studies to find these results in heterosexuals.