For Gay Men, Zero HIV Transmissions with Condomless Anal Sex and Undetectable Viral Load in PARTNER Study
BETA is reporting from the 21st International AIDS Conference this week in Durban, South Africa—bringing you the latest news, updates, and research on HIV treatment and prevention.
No HIV-negative gay men having condomless anal sex with an HIV-positive primary partner acquired HIV from their primary partner when that person had an undetectable viral load in the PARTNER study, attendees at AIDS 2016 heard yesterday. The seminal PARTNER study previously documented the very low risk of HIV transmission in mixed-status couples when the HIV-positive partner maintains an undetectable viral load. It is now the first study to provide an estimate of zero HIV transmission risk—for men who have sex with men having condomless anal sex with an undetectable partner.
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“In the absence of ART, we really would have expected over a hundred [HIV] transmissions among MSM,” said Alison Rodger, from the University College London, who presented the PARTNER study results.
The PARTNER study followed mixed-status, or “serodiscordant,” couples across 75 different clinical sites in Europe. The results presented at AIDS 2016 included a total of 340 HIV-negative partners and 282 HIV-positive partners. Participants had an estimated total of 22,273 sexual encounters during the study.
Researchers collected information from serodiscordant couples who reported condomless sex, where the HIV-negative partner was not on PEP or PrEP, and the HIV-positive partner had an undetectable viral load (less than 200 copies/mL). The study collected data over 1,238 years of follow-up (i.e., an average of 1.4 years per couple).
The median age of the HIV-negative partners in MSM couples in the study was 40. Most (83%) were white, and the median number of years they had been having condomless sex was 1.4. During the study period, 17% were diagnosed with a sexually transmitted infection (STI), about a third (33%) reported condomless sex with other partners, and the median number of condomless sex acts reported per year was 42.
Among the HIV-positive partners in MSM couples, the median age was 42. The median years on antiretroviral therapy was 5, and 18% were diagnosed with an STI during the study period. Self-reported adherence to antiretroviral therapy was high: 97% reported taking more than 90% of doses when they joined the study, and only 3% reported missing ART doses for more than four consecutive days during the study. In addition, 94% reported having an undetectable viral load and 91% had CD4 counts greater than 350 cells/mm3 when they joined the study.
Ten HIV-negative MSM seroconverted during the study—but none of the HIV transmissions were from the virally-suppressed HIV-positive primary partner. Eight of the people who seroconverted reported recent condomless sex with others apart from their primary partner. Genetic analyses of the HIV strain acquired by the people who seroconverted—compared to the genetic types of HIV their primary partners had—confirmed that HIV transmission did not occur in the primary partnership.
In this study, the rate of within-couple HIV transmission per 100 couple years of follow-up, by sex act, was:
- Any type of sex: 0 (95% confidence interval 0 – 0.84)
- Anal sex: 0 (95% confidence interval 0 – 0.89)
- Insertive anal sex: 0 (95% confidence interval 0 – 1.00)
- Receptive anal sex with ejaculation: 0 (95% confidence interval 0 – 2.70*)
- Receptive anal sex without ejaculation: 0 (95% confidence interval 0 – 1.68)
(*The larger confidence interval for receptive anal sex with ejaculation is due to the smaller sample size for this particular sex act.)
The PARTNER study is ongoing—and will continue to collect data until 2018—in order to provide even more precise estimates of HIV risk for both men who have sex with men and heterosexual couples.
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