No HIV transmission in gay couples study

Andrew Grulich at CROI 2015. Image by The Kirby Institute (

Andrew Grulich at CROI 2015. Image by The Kirby Institute (

Story via NAM (@aidsmap)


NAM is an award-winning, community-based organisation, which works from the UK. They deliver reliable and accurate HIV information across the world to HIV-positive people and to the professionals who treat, support and care for them.

An early analysis of an Australian-based study of gay male couples of opposite HIV status (serodiscordant couples) has so far seen no transmissions from the HIV-positive partner within the couple. These observational data from the Opposites Attract study concur with the interim analysis of the larger PARTNER study that was released at CROI one year ago. PARTNER reported no episodes of transmission during 16,400 episodes of anal sex (including condom-protected episodes) in gay men.

Recruitment to the new study began in late 2013 in three Australian cities (Sydney, Melbourne and Brisbane), and now also includes Bangkok in Thailand and Rio de Janeiro in Brazil. Most of the HIV-positive partners are on treatment and have an undetectable viral load.

During the study’s first year, 152 couples provided data. A total of 5905 episodes of anal sex were reported. No transmissions between couples (linked transmissions) have so far been seen in the study.

Because of the relatively small numbers enrolled so far, there is some uncertainty to these findings. Although there have been zero transmissions, this does not necessarily mean a zero chance of transmission. The researchers have calculated that in this population, the highest-likely figure for the chance of transmission during condomless anal sex with an HIV-positive partner (regardless of viral load) is 4%. The highest-likely figure when the HIV-negative partner was receptive (bottom) is 7%.

But as with PARTNER, these estimates are likely to get closer to zero as the researchers collect more data.

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