A new study in macaques suggests that antiretroviral drugs used to treat HIV could also protect people from getting the AIDS virus, especially if two drugs are taken in combination before exposure to the virus occurs. The study found that macaques which were repeatedly exposed to SHIV (a virus closely related to HIV) but received antiretroviral drugs were less likely to become infected than exposed macaques that received no anti-HIV medication. The best protection was seen in macaques that had received a combination of two drugs.