CROI 2015In mixed-HIV status couples, the combination of Truvada (tenofovir/emtricitabine) as pre-exposure prophylaxis (PrEP) and antiretroviral (ARV) treatment nearly eliminates transmissions, MedPage Today reports. Researchers reported preliminary results from the ongoing Partners Demonstration Project at the 2015 Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle.

The report concerned 1,013 mixed-status heterosexual couples in Kenya and Uganda deemed to be at very substantial risk for transmitting the virus within the couple. Neither member had taken PrEP or ARVs before. The period covered in the analysis was November 2012 through August 2014.  

The HIV-negative partner was offered PrEP until the HIV-positive partner started ARVs and then had been on them for six months. The idea was to see if PrEP would prove to be an effective “bridge,” lowering transmission risk until the time when the HIV-positive partner had a fully suppressed viral load, and therefore was vastly less infectious.

The researchers compared their results with data from the placebo arm of the earlier Partners PrEP study, which suggested that, without ARVs or PrEP, the expected number of HIV transmissions within the couples in the Partners Demonstration Project would be 39.7, for an incidence of 5.2 cases per 100 person-years.

During the period described in the CROI presentation, there were two transmissions, for an incidence of 0.2 per 100 person-years.  Therefore, PrEP and ARVs together lowered the risk of transmission by an estimated 96 percent. Both transmissions were in women who had apparently stopped taking PrEP—one had left her partner and the other remained in a partnership with a man who was not on ARVs. These results suggest that this paradigm of PrEP use—when the HIV-negative member of a couple actually adheres to PrEP until his or her partner has an undetectable viral load—would offer a risk reduction that’s likely even greater than 96 percent.

To read the MedPage Today story, click here.

To watch a webcast of the conference presentation, click here.