Consistent use of a monthly vaginal ring can significantly reduce the spread of HIV, according to new data analyses led by a researcher from the University of Washington School of Public Health. Findings were presented this week at the International AIDS Conference in Durban, South Africa.

Results show that a vaginal ring, containing an antiretroviral drug known as dapivirine, provides significant protection against HIV when used most or all of the time. Among women who used the ring most regularly, HIV risk was cut by more than half across all analyses, and in some, by 75 percent or more.

The new analyses further strengthen previous findings from the ASPIRE study, published in February in the New England Journal of Medicine, that found the dapivirine ring reduced the risk of HIV by 27 percent. The ASPIRE study — A Study to Prevent Infection with a Ring for Extended Use — enrolled 2,629 sexually active women from Malawi, Uganda, South Africa, and Zimbabwe.

“Adherence to HIV prevention strategies is not always perfect, and we know that not all women used the ring consistently, so we developed an analysis to explore the degree of HIV protection that was associated with more consistent use,” explained Elizabeth Brown, research professor of biostatistics at the UW School of Public Health, who led the new analyses of the ASPIRE data. “Across all analyses we saw high adherence was associated with significantly better HIV protection.”

Brown is also a statistician at Fred Hutchinson Cancer Research Center and Microbicide Trials Network, an international HIV/AIDS clinical trials network funded by the National Institutes of Health.

Brown and her colleagues are mindful that there are inherent limitations in these kinds of exploratory analyses and that further study will be needed to validate the results. A follow-up study to ASPIRE, called HOPE, intends to look more closely at the relationship between ring use and HIV protection.

“The goal of HOPE is to offer women a product shown to be safe and able to provide some protection against HIV,” said Jared Baeten, vice chair of global health and professor of global health and epidemiology at the School, who led the ASPIRE study and will be leading HOPE. “When we were conducting ASPIRE, we did not know whether the ring would be effective. Knowing the results of ASPIRE, it will be a totally new conversation with women in HOPE.”

For the new study, former ASPIRE participants will have the opportunity to use the dapivirine ring in the context of knowing that it is safe and can help prevent HIV. HOPE will gather additional information on the ring’s safety and how women use the ring.