HIV prevention among drug users has taken a huge step forward in a confirmation that retroviral treatments can cut the risk of transmission across the board: According to a major study published in the Lancet, addicts who took a daily tenofovir pill were 49% less likely to be infected with HIV as those who took a placebo. Addicts who took the pill regularly cut their risk by 74%, though it's unclear whether the drug prevented infections resulting from dirty needles or unprotected sex, Reuters reports.
Earlier trials found similar results for gay men, heterosexuals, and mother-to-child transmissions, reports the New York Times. "We now know [it] can work for all populations at increased risk for HIV," says a CDC official. Though 2,400 drug users were paid to be part of the study, the next step is to decide how to motivate all addicts to take the pill, an AIDS researcher tells the Times. While intravenous drug-use accounts for 8% of new HIV cases in the US, it's as high as 80% in other parts of the world. (Read more scientific study stories.)