Promising news for HIV treatment as prevention: Study finds HIV transmission rare in couples when an HIV positive partner is receiving treatment

News | Published on 26 Feb 2015

Results from the first Australian study to analyse HIV transmission risk among couples with differing HIV statuses 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 Conference on Retroviruses and Opportunistic Infections (CROI) 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 loadis undetectable. In fact, no HIV-negative man in the study has contracted HIV from his positive partner.”

The Opposites Attract study is a four-year cohort study of HIV transmission and HIV treatments in gay men in serodiscordant relationships (where one partner is HIV positive and the other is negative).  By December 2014, the Kirby Institute had enrolled 234 gay male serodiscordant couples: 135 of these were from Australia, 52 were from Bangkok, Thailand, and 47 were from Rio de Janeiro, Brazil. Of the total 234 couples enrolled, the interim analysis focused on the 152 couples who had attended at least one follow-up visit by the time of the analysis. The couples were in the study for an average time of about one year.

So far, there have been no “linked” HIV transmissions (that is, where the HIV came from the HIV-positive partner in the couple to his negative partner) 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 therisk 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 study is funded by the National Health and Medical Research Council (NHMRC) and the Foundation for AIDS Research (amfAR).

Final results from the study are expected in 2017. 


Stakeholder quotes:

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.

The impact of these early results cannot be underestimated and underscores the need for the continued regeneration of Australia’s HIV response. We know that treating HIV early now has a significant prevention impact and it is essential that service systems, policy environments and crucially, gay men, mobilise around the opportunities that this evidence provides. 

We have always said that HIV prevention is a shared responsibility between positive and negative guys. Unfortunately that has not always played out, with some positive guys made to feel marginalised on the basis of their HIV status. These research findings can also really change that landscape, and hopefully play a role in reducing HIV stigma in our community. ~  Nicolas Parkhill – Chief Executive Officer, ACON


“These results confirm the importance and effectiveness of going on highly active HIV treatments – not only for our own health as people living with HIV but for the health of our sexual partners. Stigma and fear of knowing and disclosing our HIV status remains an underlying factor driving the HIV epidemic. These findings also have a dramatic effect upon our confidence to disclosure our HIV status to sexual partners knowing that the likelihood of infecting someone is so markedly diminished when we are on treatments and maintaining an undetectable viral load. This study has had tremendous support from the HIV positive community and we have been anxiously waiting to see such great news such as this.  We have had enough fear and stigma of HIV and the entire community needs to become aware of the new facts of HIV. HIV shouldn’t stand in the way of love.” ~Brent Allan –Executive Officer, Living Positive Victoria


Laurie Legere


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