In the fight against HIV, women have been severely limited in what they can do to protect themselves against the virus and it typically involves asking an infected partner to wear a condom. In recent years, those in wealthier parts of the world have also had access to a daily preventive pill -- but the idea of such a strict regimen and the potential expense has been so daunting that few have opted to try it.

There's finally hope that a convenient and inexpensive option that puts more of the power in women's hands may be available in the not-so-distant future.

Scientists reported this week that two large-scale studies in Africa have shown that a flexible vaginal ring that women can insert themselves may be able to provide limited protection against the virus. The idea of this type of treatment first came up more than two decades ago when a number of topical microbicides in the form of gels, films, foams, and rings went into tests. To researchers' disappointment, most did not appear to work at all.

Vaginal rings typically sit near the cervix and deliver controlled-release of a drug. They have been successfully used for years for birth control and for hormone therapy. In the case of HIV, the rings are coated with an antiretroviral dapivirine and replaced every month.

In one study, which was published Monday in the New England Journal of Medicine and involved 2,629 women ages 18 to 45 in Malawi, South Africa, Uganda and Zimbabwe, the risk of transmission of the virus was reduced by 27 percent. In the other, which involved 1,959 women in the same age range in South Africa and Uganda and will be presented this week at the Conference on Retroviruses and Opportunistic Infections (CROI),  it was reduced by 31 percent.

Those numbers are promising in themselves (although lower than expected when the study was originally conceived), but the researchers also noticed something else in the data that raised their hopes even more. Among women 25 and older, the device appeared to work surprisingly better than in the younger women -- up to 56 percent in one group -- leading them to wonder whether those who didn't see a benefit just didn't use the ring the right way.

In the New England Journal of Medicine paper they noted that they may have even overestimated adherence to the therapy and theorized that some participants "may have used the ring for only a portion of the month (and possibly only for a few hours before a clinic visit)."

Mitchell Warren, executive director of AVAC, a nonprofit that focuses on HIV/AIDS prevention efforts, called on researchers to expand their trials by offering the ring to former participants who may have received a placebo.

"These studies' results are needed to help guide decisions about regulatory approval and, perhaps, eventual rollout of a monthly dapivirine ring," Warren said. "In addition, we need to look at streamlining the process of developing a combination ring that could protect against both HIV and pregnancy.”

Read more: