Dapivirine vaginal ring reduces HIV infection rates in women

A ring placed in the vagina that continuously releases experimental antiretroviral drug dapivirine reduced the risk of HIV infection in African women by 27%, according to researchers. This figure rose to 61% in women aged over 25 years, who used the ring most consistently.

“The protective effect of the dapivirine vaginal ring, as compared with placebo, was significant but not as high as hypothesised in the design of the trial,” say the researchers. “Greater HIV-1 protection was observed among subgroups of women who had evidence of higher rates of adherence than among those with lower rates of adherence.”

Researchers recruited 2,629 women aged between 18 and 45 years old from 15 sites in Malawi, South Africa, Uganda and Zimbabwe in a phase III randomised double-blind, placebo controlled trial. The average age was 26 years; 41% were married and 85% had completed secondary school education.

Some 1,313 women received a vaginal ring containing 25mg of dapivirine; another 1,316 received a placebo vaginal ring. The rings were replaced every four weeks. HIV prevention services, including HIV-1 testing and risk-reduction counselling, testing of male partners, screening and treatment of sexually transmitted infections and provision of free condoms, were given at monthly follow-ups.

During the 33-month study, 168 HIV-1 infections were recorded — 71 in the dapivirine group and 97 in the placebo group (incidence 3.3 and 4.5 per 100 person years, respectively).

The incidence of HIV-1 infection in the dapivirine group was 27% lower than in the placebo group (95% confidence interval [CI] 1 to 46; P=0.05). This figure rose to 37% (95% CI 12 to 56; P=0.007) when the researchers excluded data from two study sites where women had failed to participate fully in the research.

Higher rates of HIV-1 protection were observed among women over the age of 21 years (56%; 95% CI 31 to 71; P<0.001) but not among those 21 years or younger (−27%; 95% CI −133 to 31; P=0.45). The efficacy of HIV-1 protection differed significantly according to age, with an efficacy of 61% (95% CI 32 to 77; P<0.001) among women aged 25 years or older.

Writing their findings in The New England Journal of Medicine
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on 22 February 2016, the researchers say African women “bear a disproportionate burden of the global HIV-1 epidemic”. Latest figures show that more than half of the 25.8 million people living with HIV in Sub-Saharan Africa in 2014 were women.

The AIDS Vaccine Advocacy Coalition (AVAC), an international campaign group devoted to improving HIV prevention, welcomes the research.

“It’s clear that the dapivirine vaginal ring can be a viable option for women to protect themselves from HIV,” says Mitchell Warren, executive director of the AVAC. “The dapivirine vaginal ring might become an additional option, as additional questions are answered and regulatory agencies consider these results. In the meantime, the incredibly high HIV infection rates among women in these trials tell us that we need to make oral pre-exposure prophylaxis more widely accessible and available with urgency.”