IAS 2015Heterosexual participants in a study of Truvada (tenofovir/emtricitabine) as pre-exposure prophylaxis in Botswana apparently adhered to PrEP at very high rates, and there were no new HIV infections among them. The 229 participants in this open-label extension (OLE) phase of the TDF2 trial also reported taking fewer sexual risks during the year-long study. Results from the trial were presented at the 8th International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention in Vancouver, British Columbia.

There was no comparison, or control, group in this OLE trial, so the investigators will not publish an effectiveness rate estimating how well PrEP protected the participants against HIV. But when it comes to predicting how heterosexuals will likely adhere to PrEP outside of a study, the OLE phase may provide a more accurate projection than the randomized, double-blind, placebo-controlled phase of TDF2 that preceded it, and which was published in 2011. The OLE phase was set up to more closely resemble a real-world scenario, because, in contrast to the placebo-controlled trial, participants knew they were taking Truvada and were not paid to be in the study.

Twenty-two percent of Botswanans ages 15 to 49 are HIV positive. In the previous placebo-controlled trial, which showed that PrEP had a population-level effectiveness of 62 percent, 1.2 percent of those receiving Truvada and 3.1 percent of those taking the placebo contracted HIV each year.

The OLE participants made monstly study visits. During the study, the number of reported sex acts during the previous month declined by 12 percent and the number of sex acts without a condom fell by 39 percent. Overall, the male participants reported an average of 1.03 sexual partners and the women reported 0.87 during the month prior. Men reported an average of 1.7 condomless sex acts per month, while women reported 1.3.

At four quarterly follow-up visits, the researchers collected blood samples for dried blood spot testing, which can determine if an individual has taken PrEP during the previous few days, from a random sample of 120 participants. The participants had detectable drug in their systems at an average of 93 percent of the visits: women at 87 percent of visits and men at 96 percent. A respective 95 percent, 93 percent, 94 percent and 91 percent of the participants tested had detectable drug at each visit.

Editor’s note: A previous version of this article incorrectly stated that the participants made study visits every three months, instead of monthly, which is correct.