Results from the first Australian study to analyze HIV transmission risk among serodiscordant couples (where one is HIV negative and one is positive) suggest that HIV positive men who are on treatment and have an undetectable viral load are not transmitting the virus to their partners.
Researchers from the Kirby Institute at UNSW Australia today presented results from the first two years of the Opposites Attract study at the annual CROI 2015 Conference in Seattle, Washington, U.S.A.
“These are very exciting results that seem to mirror findings from other important international studies of heterosexual couples, which have provided strong evidence that treatment as prevention works,” said Professor Andrew Grulich, chief investigator on the study. “Essentially, what we are seeing among the gay couples enrolled in Opposites Attract is that HIV transmission is quite unlikely when someone’s viral load is undetectable. In fact, no HIV-negative man in the study has contracted HIV from his positive partner.”
So far, there have been no “linked” HIV transmissions among couples enrolled in the study. “This means that we have found an HIV transmission rate of zero within the Opposites Attract study couples to date,” said Professor Grulich.
Although preliminary results are promising, researchers caution that more evidence is needed to better understand the risk involved in having sex without condoms when an HIV-positive partner has undetectable viral load.
“The true risk of transmission could be anywhere between zero and 4.2% per year, with a very small chance that the per-year risk could be higher than 4.2%,” said Professor Grulich. “We still need more gay couples to enroll in Opposites Attract, and we need to continue following up with the couples in the study before we can produce a more conclusive result to fully answer the question of how much HIV treatment reduces HIV transmission between partners in gay, serodiscordant couples.”
“The results from the Opposites Attract study are incredibly exciting and add further promise to new ways of delivering HIV prevention here in Australia. While we have had international studies increasingly demonstrating that treatment as prevention works, we now have an Australian study clearly indicating population health benefits for gay men, ” said ACON CEO Nicolas Parkhill.
Final results from the study are expected in 2017.
The study is funded by the National Health and Medical Research Council (NHMRC) and the Foundation for AIDS Research (amfAR).
Find out more about the Opposites Attract Study by visiting their website: www.oppositesattract.net.au