July 20, 2015
Written by NIH
This press release originally appeared on NIH’s website.
Antiretroviral treatment that consistently suppresses HIV is highly effective at preventing sexual transmission of the virus in heterosexual couples where one person is HIV-infected and the other is not, investigators report today at the 8th International AIDS Society Conference on HIV Pathogenesis, Treatment & Prevention (IAS 2015) in Vancouver, Canada. The finding comes from the decade-long HPTN 052 clinical trial funded primarily by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, and conducted by the NIH-funded HIV Prevention Trials Network (HPTN).
In 2011, the HPTN 052 study investigators reported a breakthrough: Starting HIV treatment early, when the immune system is relatively healthy, reduced the risk of sexually transmitting the virus to an uninfected partner by 96 percent over 18 months. Based on additional data gathered since 2011, today’s finding unequivocally demonstrates the enduring power of HIV-controlling antiretroviral therapy to greatly reduce sexual transmission of the virus.
“The study now makes crystal clear that when an HIV-infected person takes antiretroviral therapy that keeps the virus suppressed, the treatment is highly effective at preventing sexual transmission of HIV to an uninfected heterosexual partner,” said NIAID Director Anthony S. Fauci, M.D. “For heterosexuals who can achieve and maintain viral suppression, the risk to their partners is exceedingly low.”
The HPTN 052 trial was designed to evaluate whether antiretroviral therapy reduces sexual transmission of HIV. Beginning in April 2005, the study enrolled 1,763 heterosexual couples ages 18 or older in Botswana, Brazil, India, Kenya, Malawi, South Africa, Thailand, the United States and Zimbabwe. Each couple included one partner with HIV infection and one without. Infected participants were assigned at random either to start antiretroviral therapy right away, while their immune system was relatively healthy, or to delay starting treatment until their immune system weakened or they developed an AIDS-defining illness, consistent with World Health Organization guidelines at the time. All participants received condoms and counseling on how to protect their partners from sexual transmission of HIV.
Once the investigators reported their landmark data in 2011, all infected study participants were offered the opportunity to begin antiretroviral therapy right away, and the trial continued for another four years, concluding this spring. At the end of the study, 1,171 couples remained in the trial.
Investigators report today that starting antiretroviral therapy early reduced HIV transmission by 93 percent over the course of the study. Only eight cases of HIV transmission occurred in uninfected partners of HIV-infected participants who received antiretroviral therapy. Four of these infections were diagnosed shortly after the start of treatment. In these cases, the virus most likely was transmitted just before antiretroviral therapy began or right after it commenced, before treatment had fully suppressed HIV replication. The other four infections occurred in study participants for whom treatment no longer was working and the virus was replicating. Treatment failure may have occurred because HIV-infected participants did not take their antiretroviral drugs as prescribed or had an HIV strain that was resistant to one or more of the drugs in their treatment regimen.