FOR SOME WOMEN, the power to negotiate safe sex is not always within their control. Whether through coercion, force or partner reticence, women’s HIV prevention efforts are usually limited unless their male partners opt to wear a condom.

But new results from two large clinical trials have shown that a ring that slowly secretes an antiretroviral drug into the vagina could reduce around 6-in-10 HIV infections in women, with a promising proof of concept that could be built upon to increase the prevention odds.

Led by the International Partnership for Microbicides (IPM), the Ring Study was a clinical trial designed with the goal to determine if IPM’s monthly vaginal ring could be successful in reducing HIV infection in women, and whether it was safe for long-term use. 

Participants in the study were randomly assigned to use either the drug-impregnated ring or a placebo ring. The treated ring contained 25mg of the antiretroviral drug dapivirine, while the placebo ring was untreated. Participants remained in their assigned ring groups for the whole study, and rings were changed out every 28 days.

The women participated in the study for two years to examine the long term effects. 

Another study, called ASPIRE, sampled 2,629 HIV-negative women between the ages of 18 and 45, and they stayed in the study for a period of a year. 

Results from both trials found that the ring reduced the risk of acquiring HIV by 27% overall, with prevention rates as high as 61% in women over 25, and almost no prevention effect on women under 25 years old.

According to Dr. Jared Baeten who led the ASPIRE study, “the hope was to find something that could be usable enough by women that it would provide H.I.V. protection, and that’s what we got… it gives me tremendous optimism.”

But there are strong concerns about the ring’s effectiveness in younger women. According to Baeten:

“Our results make it very clear that we must do more to address the unique needs of younger women in our study. Why did the ring not work for them? We need to understand whether it is adherence alone or biological or physiological factors”– Dr. Jared Baeten, ASPIRE study lead

As one explanation for the failure in younger women, researchers pointed to poor adherence as a key concern and a contributor to the lack of effectiveness in the younger age groups.

Since dapivirine levels decrease each day, researchers could determine who complied with the suggested treatment protocol by measuring the drug levels in the used rings. Researchers were able to conclude that the ring had been worn at least eight hours before the drug level measurement, but that several of the younger participants were not wearing the rings for the full 28 days as intended. 

The results suggest that with better education on how to use the ring, rates of adherence could be vastly improved.

“Both ASPIRE and the Ring Study raised important scientific questions about the susceptibility of very young women with HIV and their willingness to use prevention products. Further research may address these knowledge gaps”, said Sharon L. Hillier, Ph.D., of the University of Pittsburgh and principal investigator of the Microbicide Trials Network.

Despite the lack of HIV protection for younger age groups, researchers plan to begin product license in early 2017 for the ASPIRE and Ring trials if all goes well in a follow-up, open-label study.

“IPM will seek regulatory approval for the monthly dapivirine ring and work with partners to determine its role in strengthening HIV prevention efforts. We are also hopeful that we can learn more about how to help women who want to use the ring, do so consistently” – Dr. Zeda Rosenberg, founding Chief Executive Officer of IPM

Female-controlled HIV prevention interventions are welcome news for the Caribbean, which currently records the second-highest prevalence of HIV after sub-Saharan Africa. There are currently 250,000 people living with HIV/AIDS in the region, of which 120,000 are women aged 15+. New prevention methods such as the vaginal ring may significantly impact their health outcomes.

• Editing and additional reporting by Jovan Reid

Gianna Medina, Health Desk

Gianna Medina, an AMG Health Writer, is an MPH/MBA candidate at Benedictine University