Those women who adhered well to an antiretroviral (ARV)-containing vaginal ring benefited from a significant reduction in HIV risk. Findings from the placebo-controlled MTN-020/ASPIRE study were initially presented, and caused quite a stir, at the 2016 Conference on Retroviruses and Opportunistic Infections (CROI) in Boston. In that analysis, the ring reduced the risk of HIV by 27 percent overall and by 37 percent when excluding the results from two study sites where adherence among the female participants was lower.

The new analysis, which included data on 2,359 of the 2,629 female participants, was presented at the 21st International AIDS Conference in Durban, South Africa (AIDS 2016).

The rings contained 25 milligrams of the ARV dapivirine. Since previous research showed that four weeks of continuous use of the rings resulted in their emission of about 4 mg of the drug, the researchers qualified women as having adhered poorly if they returned a ring at their regular study visit, scheduled every four weeks, that had 22 mg or more of dapivirine still in the ring. (The researchers started testing the drug levels in the returned rings one year into the trial.) Women were also considered to have poor adherence if they did not return the ring at a visit or did not have access to a ring.

Compared with women who received the placebo, those who adhered well had a 56 percent lower risk of contracting HIV. Those women who used the ring at the highest level had a 75 percent or greater reduction in risk.

Those who had poor adherence essentially received no benefit from the ring.

“We are encouraged by these new analyses, which further support that the dapivirine ring could be an important option for women who urgently need new tools to protect themselves from HIV,” Zeda Rosenberg, ScD, founder and chief executive officer of the International Partnership for Microbicides, said in a press release. “While IPM seeks regulatory approval for the ring, we will continue to work to understand how we can best support women to use it consistently, and advance research to expand women’s options with additional new methods that make sense for their lives and needs.”

To read a press release about the study, click here.