From the New York Times:
In a development that could change the battle against AIDS, researchers have found that taking a daily antiretroviral pill greatly lowers the chances of getting infected with the fatal virus. In the study, published Tuesday by the New England Journal of Medicine, researchers found that the hundreds of gay men randomly assigned to take the drugs were 44 percent less likely to get infected than the equal number assigned to take a placebo. But when only the men whose blood tests showed they had taken their pill faithfully every day were considered, the pill was more than 90 percent effective
Read the full article on the New York Times Website.