The Kirby Institute at UNSW Australia welcomes early results from the PARTNER study, which has found that HIV positive gay men who are on treatment and have undetectable viral load are not transmitting HIV to their partners.
Led by the University of Copenhagen, the PARTNER study examines the risk of sexual transmission when an HIV positive person is on treatment and when the couple have unprotected sex with each other. Results of the first two years of the study were presented at the Conferences on Retroviruses and Opportunistic Infections in Boston, USA this week.
Although previous research in heterosexual couples has shown that when the HIV-positive partner is on anti-HIV treatments and has undetectable viral load, the risk of transmitting HIV to their HIV-negative partner is reduced by 96 per cent,this is the first study to look at similar data from gay couples. Investigators reported that no HIV transmissions occurred in 282 HIV serodiscordant gay couples (where one man is HIV-negative and the other is HIV-positive) with undetectable viral load (less than 200 copies per ml) who had unprotected anal sex over an average period of one year.
"These exciting results directly demonstrating the efficacy of HIV treatment as prevention in gay men are very encouraging", said Professor Andrew Grulich, Program Head at the Kirby Institute. "However, I echo the cautious optimism expressed by the PARTNER team. It is important to note that although no new HIV infections were seen in early study results, HIV transmission could occur in up to one per cent of gay couples per year having unprotected anal sex. In those couples at highest risk, where the HIV negative partner has unprotected receptive anal sex with ejaculation with his HIV positive partner, the risk could be higher, with a potential HIV transmission rate of up to four per cent per year."
The PARTNER study and the Kirby Institute's Opposites Attract study are the only two studies in the world currently looking at HIV transmission risk in gay male serodiscordant couples.
In Australia, the Kirby Institute's Opposites Attract study has been recruiting in New South Wales, Victoria and Queensland over the last two years and more than 100 gay couples have been enrolled. The study is soon to commence recruitment in Brazil and Thailand.
"We salute the commitment of the gay couples who are helping us answer important questions about preventing HIV transmission and encourage many more to join our study," said Professor Grulich. "These early results make it imperative that studies of HIV transmission and viral load in HIV serodiscordant gay couples are expanded."