Mixed-HIV status heterosexual couples who received Truvada (tenofovir/emtricitabine) as pre-exposure prophylaxis (PrEP) as a “bridge” to HIV treatment lowered their transmission risk by 95 percent. Researchers from the Partners PrEP study of 1,013 couples in Kenya and Uganda, in which 67 percent of the female partners were the ones living with the virus and the median age of participants was 29, presented their findings at the 21st International AIDS Conference in Durban, South Africa (AIDS 2016).

The HIV-negative participants were provided PrEP as a so-called bridge, until their HIV-positive partner had started ARVs and had been on them for six months. HIV treatment was recommended following national guidelines, which initially were to start treatment when CD4s dropped below 350 but then switched during the study to universal treatment for HIV-positive people in a partnership with an HIV-negative individual.

The couples were followed for two years.

Looking at a random sample of HIV-negative partners while they were receiving PrEP, the researchers found detectable tenofovir, one of the drugs in Truvada, in 82 percent (483 of 587) of the plasma samples, which they gave at each study visit.

Ninety-two percent of the HIV-positive partners started treatment for the virus within 24 months of the study. Ninety percent of them achieved viral suppression, defined as a viral load below 400.

Four partners contracted HIV. This is compared with mathematical modeling, based upon the previous placebo arm of the study, predicting that there would have been 83 transmissions between partners without PrEP and if the HIV-positive partners waited until their CD4s dropped below 350 to start ARVs. This meant that the study’s protocol of PrEP as a bridge to the positive partner passing six months on treatment lowered the risk of HIV transmission within couples by an estimated 95 percent, a risk reduction researchers characterized as “near elimination.”