Adherence to the dapivirine vaginal ring, a topical HIV-1 agent to prevent HIV infection, improved over time, according to the results of a recent study.1

The vaginal ring is an investigational pre-exposure prophylactic (PrEP) agent that is inserted in the vagina. The silicone matrix ring is loaded with a microbicidal agent, says Marla Husnik, PhD, MS, associate director at The Janssen Pharmaceutical Companies of Johnson & Johnson in Raritan, NJ.

The ring was developed through Janssen and the International Partnership for Microbicides (IPM). It is used only for HIV prevention.

“This particular ring does not have a dual agent [for contraception] in it,” Husnik says. “However, IPM is currently working on clinical studies that are incorporating a dual pregnancy prophylactic agent along with the dapivirine ring.”

Husnik and colleagues wanted to study correlates to adherence among people using the ring.

“We were really interested in using this clinical trial — a very large one — to evaluate what are the sorts of correlates to some very objective measures of adherence,” Husnik explains. “There were other studies that were done on this population of women in Africa that were much more subjective in nature, but we were interested in using objective measures of adherence.”

Research participants’ plasma measurements were checked quarterly to evaluate dapivirine levels. The vaginal rings were collected at the clinical site and delivered monthly.

“They were instructed to bring the rings back after a one-month period, even though the plasma was only collected quarterly,” Husnik explains. “The monthly ring returns allowed us to analyze how much of the dapivirine drug was remaining in the ring.”

The Time Effect

Researchers found there was a time effect in the use of the ring. “We found that the time on study and calendar time were highly correlated with adherence,” Husnik says.

This suggested women experienced a learning period about how to use the ring. “Then, there was a maintenance period where women became familiar with the ring,” Husnik says. “When she became comfortable with it, adherence went up.”

The clinical trial continued for more than seven years, and not all women were enrolled at the same time. This enabled investigators to study the calendar effect. The association with calendar time appeared to reflect implementation of a real-time adherence monitoring intervention.1

“Beginning with the three- to six-month period, as a reference, researchers compared this period with the nine- to 12-month period of being in the study, and also with 15-33 months,” Husnik explains. “What we saw, compared to the reference group of three to six months, was an increase in adherence for those later time periods. The longer they were on the study, the more apt they became to use it.”

Another correlate to adherence was whether their primary partner knew they were taking part in the study. If the partner knew about their study participation, they were more likely to use the ring, Husnik says.

The European Medicines Agency issued an opinion supporting the use of the dapivirine ring for PrEP by cisgender women, ages 18 and older, in developing countries.2

“I know there will be a submission and a review by the Food and Drug Administration, as well,” Husnik says.

The chief benefit of the dapivirine ring is that it is a rare HIV prevention strategy that is designed for women that they can use discreetly. “A woman can use this vaginal ring, and her partner will not know it,” she explains. “She will not be subjected to having to carry pills around.”

For some women, there is stigma associated with using HIV medication — either for treatment or for PrEP — and the ring avoids that stigma.

“This would be a very discreet way of protecting herself,” Husnik says.


  1. Husnik MJ, Brown ER, Dadabhai SS, et al. Correlates of adherence to the dapivirine vaginal ring for HIV-1 prevention. AIDS Behav 2021 Jun 11. doi: 10.1007/s10461-021-03231-x. [Online ahead of print].
  2. International Partnership for Microbicides. In milestone for women’s HIV prevention, European Medicines Agency adopts positive opinion on monthly vaginal ring to reduce HIV risk. July 24, 2021.