This photo provided by the International Partnership for Microbicides shows a ring that is coated with an anti-AIDS drug designed for women to insert into the vagina once a month to reduce the risk of HIV infection. Researchers say women who inserted a vaginal ring coated with an anti-AIDS drug once a month were partially protected against HIV infection. Two large studies in Africa found the effect was modest, reducing overall HIV infection by about a third. But surprisingly, the ring worked far better in women 25 and older, leaving researchers wondering if younger women who got little to no benefit simply didn't use the device properly. (Andrew Loxley/International Partnership for Microbicides via AP) Photo: Andrew Loxley