Further evidence that taking anti-HIV drugs stops gay men passing on the virus to sexual partners has been called a "powerful message" which needs to be spread more widely. BBC News reports that a study of nearly 1,000 gay male couples found no cases of HIV transmission over eight years. This was due to treatment reducing the virus to very low levels in the body.
"Undetectable equals untransmittable" should be basic HIV knowledge for everyone, experts said.
The European study followed 972 gay male couples – where one was living with HIV and taking antiretroviral therapy (ART) and the other was HIV negative – over eight years, from 2010-2017. There were no cases of HIV being passed within the couples over that time. And the researchers say that around 472 cases of HIV are likely to have been prevented.
In total, the couples reported having anal sex without condoms a total of 76,088 times. Although 15 men did become infected with HIV during the study, genetic testing showed that none of the viruses came from their main partner. "Our findings provide conclusive evidence that the risk of HIV transmission through anal sex when HIV viral load is suppressed is effectively zero," the researchers said.
Professor Alison Rodger, study author and professor of infectious diseases at University College London, said in the report that anal sex was known to have the highest risk of transmission, but gay men should be reassured. "This powerful message can help end the HIV pandemic by preventing HIV transmission, and tackling the stigma and discrimination that many people with HIV face."
She called for all people living with HIV to have access to testing and effective treatment.
Deborah Gold, CEO of NAT (National AIDS Trust) said more should be done to get the message out to healthcare workers and the general public. "There needs to be a much better understanding of how HIV is and isn't transmitted, and the fact that treatment stops transmission, in the National Health Service (NHS) and beyond. We think this is vital to addressing stigma."
The report says previous research has shown zero risk for heterosexual couples of passing on the virus, when one person is taking HIV treatment, prompting UNAIDS to launch its undetectable = untransmittable campaign.
Dr Ford Hickson, from the London School of Hygiene and Tropical Medicine, said the study confirmed that if people suppress their HIV with antiretroviral therapy, they "cannot pass their virus to other people during sex, whatever kind of sex they have".
In the study, the men with HIV had been taking antiretroviral therapy for an average of four years before it began, making the virus undetectable – defined as fewer than 200 copies per ml of blood.
Most people reach this level after taking daily HIV treatment for six months.
Background: 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. The aim of the second phase of the PARTNER study (PARTNER2) was to provide precise estimates of transmission risk in gay serodifferent partnerships.
Methods: The PARTNER study was a prospective observational study done at 75 sites in 14 European countries. The first phase of the study (PARTNER1; Sept 15, 2010, to May 31, 2014) recruited and followed up both heterosexual and gay serodifferent couples (HIV-positive partner taking suppressive ART) who reported condomless sex, whereas the PARTNER2 extension (to April 30, 2018) recruited and followed up gay couples only. At study visits, data collection included sexual behaviour questionnaires, HIV testing (HIV-negative partner), and HIV-1 viral load testing (HIV-positive partner). If a seroconversion occurred in the HIV-negative partner, anonymised phylogenetic analysis was done to compare HIV-1 pol and envsequences in both partners to identify linked transmissions. Couple-years of follow-up were eligible for inclusion if condomless sex was reported, use of pre-exposure prophylaxis or post-exposure prophylaxis was not reported by the HIV-negative partner, and the HIV-positive partner was virally suppressed (plasma HIV-1 RNA <200 copies per mL) at the most recent visit (within the past year). Incidence rate of HIV transmission was calculated as the number of phylogenetically linked HIV infections that occurred during eligible couple-years of follow-up divided by eligible couple-years of follow-up. Two-sided 95% CIs for the incidence rate of transmission were calculated using exact Poisson methods.
Findings: Between Sept 15, 2010, and July 31, 2017, 972 gay couples were enrolled, of which 782 provided 1593 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).
Interpretation: Our results provide a similar level of evidence on viral suppression and HIV transmission risk for gay men to that previously generated for heterosexual couples and suggest that the risk of HIV transmission in gay couples through condomless sex when HIV viral load is suppressed is effectively zero. Our findings support the message of the U=U (undetectable equals untransmittable) campaign, and the benefits of early testing and treatment for HIV.
Alison J Rodger, Valentina Cambiano, Tina Bruun, Pietro Vernazza, Simon Collins, Olaf Degen, Giulio Maria Corbelli, Vicente Estrada, Anna Maria Geretti, Apostolos Beloukas, Dorthe Raben, Pep Coll, Andrea Antinori, Nneka Nwokolo, Armin Rieger, Jan M Prins, Anders Blaxhult, Rainer Weber, Arne Van Eeden, Norbert H Brockmeyer, Amanda Clarke, Jorge del Romero Guerrero, Francois Raffi, Johannes R Bogner, Gilles Wandeler, Jan Gerstoft, Felix Gutiérrez, Kees Brinkman, Maria Kitchen, Lars Ostergaard, Agathe Leon, Matti Ristola, Heiko Jessen, Hans-Jürgen Stellbrink, Andrew N Phillips, Jens Lundgren
[link url="https://www.bbc.com/news/health-48124007"]BBC News report[/link]
[link url="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)30418-0/fulltext"]The Lancet abstract[/link]