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Vaginal ring for HIV prevention effective and acceptable
Roger Pebody, 2016-09-02 07:20:00

An updated adherence analysis from the ASPIRE study indicates that consistent users of a vaginal ring containing dapivirine experienced 65% fewer infections, the 21st International AIDS Conference (AIDS 2016) in Durban, South Africa heard last month. Some additional analyses suggested a higher level of effectiveness. Moreover, African women who took part in the study told researchers that they liked the product, found it easy to use and preferred it to possible alternatives such as tablets or vaginal gels.

The ASPIRE study evaluated the effectiveness of a vaginal ring impregnated with the anti-HIV drug dapivirine. The ring, which is similar to devices used for contraception, is designed to be worn inside the vagina for a month at a time; women can insert and remove it themselves. The study recruited 2629 women in in Malawi, South Africa, Uganda and Zimbabwe.

The headline findings, released in February, were somewhat disappointing – an overall reduction in infections of 27%. But this masked a higher level of effectiveness for the older study participants, who may have had higher levels of adherence than the younger participants. Stratified by age, the vaginal ring had zero effectiveness for women aged 18-21; reduced infections by 56% in women aged over 22-26; and reduced infections by 51% in women aged 27 and over.

In Durban, Elizabeth Brown of the University of Washington presented a new analysis which attempted to correlate effectiveness with different levels of adherence. Whereas previous analyses have evaluated adherence by measuring levels of dapivirine in the blood, this could reflect the ring only being inserted the day before a clinic visit. The new analysis looked at the level of drug left behind in rings that were returned to the researchers after use, giving a better indication of adherence throughout the month.

Before use, the rings contain 25mg of dapivirine. As a ring that has been worn for a full month should have 20-21mg of drug remaining, any level below 22mg was treated as indicating medium to high adherence. A ring with 23.5mg or more of drug indicated non-adherence.

  • Periods of time with non-adherence represented 33% of follow-up. As could be expected, there was not a statistically significant reduction in HIV infections during these periods.
  • Periods of time with medium to high adherence represented 42% of follow-up. Rings used this much reduced HIV infections by 65%, compared to placebo.

The researchers also conducted additional analyses, which attempted to adjust for the actual length of time between study visits and examined adherence two or three months prior to HIV infection (rather than just one month prior). These suggested that effectiveness for women with the highest level of adherence might be 75% or 92%. Moreover periods of non-adherence appeared to represent a smaller proportion (20%) of time.

“Across multiple analyses, there is a statistically significant relationship between ring use and HIV protection,” the researchers concluded. “These analyses provide evidence suggesting a dose-response relationship between ring use and HIV acquisition.”