A three-country observational study, Opposites Attract, found no genetically linked HIV transmissions in gay couples when the HIV-positive partner had an undetectable viral load . The 343-couple study recorded more than 12,000 condom-free anal sex acts in which the HIV-negative partner was protected only by his positive partner's undetectable load--not by PrEP. The results confirm findings in the European PARTNER Study of gay couples .
Opposites Attract recruited HIV-discordant couples (one partner HIV-negative/one partner HIV-positive) from three Australian cities, from Rio De Janeiro, Brazil, and from Bangkok, Thailand. The positive partner did not have to be taking antiretroviral therapy (ART), and the negative partner could use PrEP. Couples had to have regular anal sex, and there were no condom requirements. Couples made study visits twice a year. During the visit, researchers measured the positive partner's viral load and tested the negative partner for HIV infection.
The researchers signed up 358 couples, 343 of which had at least one follow-up visit. Follow-up ended on December 31, 2016. Australia provided 157 couples, Bangkok 105, and Rio 96. Follow-up averaged about 1.5 years per couple.
About three quarters of HIV-positive partners took ART throughout follow-up, and most of the rest started therapy during the study period. Three quarters of the positive group had an undetectable viral load throughout follow-up, and about three quarters of couples had anal sex without condoms during the study. About one third of HIV-negative partners used PrEP at some point during the study.
No HIV-negative man became infected with the HIV of his positive partner. During the study there were more than 12,000 bouts of condom-free anal sex in which the positive partner had an undetectable viral load (below 200 copies) and the negative partner was not taking PrEP. The researchers estimated that the risk of HIV transmission during condom-free anal sex ranged from 0 to 1.56% per year, somewhat lower than the estimate in the PARTNER Study (0 to 2.70% per year).
Combining Opposites Attract and PARTNER data, the researchers counted 34,911 acts of condom-free anal sex during which the positive partner had an undetectable viral load and the negative partner did not use PrEP. The Opposites Attract team believes their primary finding "provides further evidence to add to previous studies that HIV transmission when someone's viral load is undetectable is extremely unlikely, if not impossible." They proposed that "condomless sex with [an] undetectable viral load is a form of safe sex." But they cautioned that viral load remains detectable in the first months after a person starts ART, so HIV transmission may be possible in that period.
- Bavinton B, Grinsztejn B, Phanuphak N, et al. HIV treatment prevents HIV transmission in male serodiscordant couples in Australia, Thailand and Brazil. 9th IAS Conference on HIV Science (IAS 2017), July 23-26, 2017, Paris. Abstract TUAC0506LB.
- Rodger A. Association between sexual activity without condoms and risk of HIV transmission in serodifferent couples when the HIV-positive partner is using suppressive antiretroviral therapy: the PARTNER study. 21st International AIDS Conference (AIDS 2016). July 18-22, 2016. Durban, South Africa. Abstract TUAC0206. http://www.natap.org/2016/IAC/IAC_08.htm