Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study. Lancet
The level of evidence for HIV transmission risk through condomless sex in serodifferent gay couples with the HIV-positive partner taking virally suppressive antiretroviral therapy (ART) is limited compared with the evidence available for transmission risk in heterosexual couples. In the first phase of the PARTNER study, some evidence on transmission risk in gay men was provided but follow-up in these studies was not sufficient to exclude a significant upper limit of risk around the study estimates of zero transmissions in gay men. In PARTNER2, Rodger et al. on behalf of the PARTNER study group aimed to fill this gap and to produce a similar level of evidence for transmission risk through condomless anal sex between men with suppressive ART (defined as HIV-1 RNA viral load
Between Sept 15, 2010, and July 31, 2017, 972 gay couples were enrolled, of which 782 provided 1’593 eligible couple-years of follow-up with a median follow-up of 2·0 years (IQR 1·1–3·5). At baseline, median age for HIV-positive partners was 40 years (IQR 33–46) and couples reported condomless sex for a median of 1·0 years (IQR 0·4–2·9). During eligible couple-years of follow-up, couples reported condomless anal sex a total of 76’088 times. 288 (37%) of 777 HIV-negative men reported condomless sex with other partners. 15 new HIV infections occurred during eligible couple-years of follow-up, but none were phylogenetically linked within-couple transmissions, resulting in an HIV transmission rate of zero (upper 95% CI 0·23 per 100 couple-years of follow-up).
In conclusion, the results from the PARTNER studies support wider dissemination of the message of the U=U campaign (undetectable equals untransmittable) that risk of transmission of HIV in the context of virally suppressive ART is zero. This dissemination is necessary to promote the benefits of early testing and treatment and to tackle stigma, discrimination, and criminalization laws that continue to affect HIV-positive people. However, U=U is only easy to apply when HIV-positive people have access to testing, effective treatment, viral load monitoring to levels of less than 200 copies per mL, and support to reach and maintain viral suppression.