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PARTNER-2 Study No HIV transmissions in 8 years when gay HIV+ partner has undetectable load
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22nd International AIDS Conference, Amsterdam, Netherlands, July 23-27, 2018
Mark Mascolini
In 783 gay male couples tracked for 8 years, no HIV-positive partner with an undetectable viral load infected his HIV-negative sex mate through 77,000 episodes of anal sex without condoms [1]. These PARTNER2 study results confirm findings in PARTNER1, in which 65% of HIV-different couples were heterosexual [2]. "An undetectable viral load on HIV treatment renders an individual sexually noninfectious," the researchers concluded.
Among 1166 HIV-different couples in PARTNER1, 11 HIV-negative partners (including 10 gay/bisexual men) picked up HIV, but none of the new infections could be genetically linked to the HIV-positive partner [2]. Still, the upper 95% confidence interval in gay couples exceeded that in heterosexual couples (0.84 versus 0.46 per 100 couple-years), a finding raising concern about higher transmission risk in gay couples practicing condomless sex.
To provide more precise estimates of HIV transmission risk in gay couples with a virally suppressed HIV-positive mate, PARTNER2 researchers conducted this new observational analysis from September 2010 to April 2018 [1]. Partners with HIV took antiretroviral therapy and had a viral load below 200 copies, and couples had anal sex without a condom. Researchers collected data at a baseline visit then every 6 to 12 months, including HIV testing of the negative partner and viral load measurement of the positive partner. HIV-negative partners did not take pre- or postexposure prophylaxis (PEP or PrEP) during study periods.
The analysis involved 783 gay couples at 55 clinics in 14 European countries; 89% of initially HIV-negative men were white. When they entered the study, HIV-negative men had a median age of 38 years and had practiced condomless sex for a median of 1 year. During 1.6 years of follow-up, these men had a median of 43 condomless sex acts per year and an estimated total 76,940 sexual encounters without condoms. Initially HIV-positive men had a median baseline age of 40 years, had taken ART for a median of 4 years, and 98% reported at least 90% antiretroviral adherence. Only 2% of HIV-positive men said they missed ART for more than 4 consecutive days.
During the study period 15 initially HIV-negative men tested positive for HIV, and three quarters of them reported recent condom-free sex with someone other than their study partner. Genetic testing of HIV from the 15 partner pairs showed that none of the infecting viruses matched a partner's virus. In other words, these 15 men got infected by someone other than their study partner.
The overall upper limit of the 95% confidence interval for acquiring HIV was 0.23 per 100 couple-years, lower than the 0.46 for heterosexual couples in PARTNER1. But the upper limit of the 95% confidence interval varied according to the type of sex the HIV-negative PARTNER2 man reported: 0.23 for any sex, 0.24 for anal sex, 0.27 for insertive anal sex, 0.43 for receptive anal sex without ejaculation, 0.57 for receptive anal sex with ejaculation, and 2.74 for any sex with a sexually transmitted infection.
The PARTNER2 researchers believe their results "give equivalence of evidence for gay men as for heterosexual couples and indicate that the risk of HIV transmission when HIV viral load is suppressed is effectively zero."
References
1. Rodger A, Cambiano V, Bruun T, et al. Risk of HIV transmission through condomless sex in MSM couples with suppressive ART: the PARTNER2 Study extended results in gay men. AIDS 2018: 22nd International AIDS Conference, Amsterdam, Netherlands, July 23-27, 2018. Abstract WEAX0104LB.
2. Rodger AJ, Cambiano V, Bruun T, et al; PARTNER Study Group. Sexual activity without condoms and risk of HIV transmission in serodifferent couples when the HIV-positive partner is using suppressive antiretroviral therapy. JAMA. 2016;316:171-181.
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