Final Results of the PARTNER2 Study Confirm: U=U

Final Results of the PARTNER2 Study Confirm: U=U
Eight years, 1,000 serodiscordant gay male couples, and zero HIV transmissions
by Hank Trout

The final results of the groundbreaking PARTNER study, published on May 2, 2019, in the respected medical journal The Lancet, confirms that having an undetectable viral load and being on HIV treatment renders an individual sexually non-infectious.

The final publication of the results, which were first presented at the AIDS2018 conference in Amsterdam in July 2018, provides and acknowledges the scientific evidence for how effectively HIV treatment prevents sexual transmission. The study reports zero HIV transmissions over eight years in serodiscordant gay couples not using condoms. The results are important to support improving the quality of life for HIV positive people and their partners globally. The results of the PARTNER2 study can have incredible impact on the lives of people living with HIV and form a powerful message to address HIV-related stigma.

Almost 1,000 serodiscordant gay male couples from fourteen different European countries participated in the PARTNER2 study from September 2010 to April 2018, with the HIV-positive partner on effective HIV treatment with viral load less than 200 copies/mL. The PARTNER2 study enrolled only couples who had already decided not to use condoms on a regular basis. Participants also completed questionnaires every six months describing how often they had sex. The HIV-positive partner continued to receive HIV viral load monitoring and the negative partner received HIV testing every six to twelve months. After eight years of monitoring, and approximately 77,000 times that couples had sex without using condoms, there were zero HIV transmissions within the couples in the study. The results showed that ART is just as effective for gay couples as an earlier phase of the study proved it was for heterosexual couples, confirming that an undetectable viral load on HIV treatment renders an individual sexually non-infectious.

The results support the Prevention Access Campaign’s global Undetectable Equals Untransmittable (U=U) campaign to foster greater awareness of how effective ART can help people have sex without any fear of passing on HIV. To date, more than 850 organizations across nearly 100 countries have joined U=U, an unprecedented grassroots movement that is backed by science and seeking to change the lives of people living with and effected by HIV. The PARTNER2 study confirms that U=U.

Carl Dieffenbach, Bruce Richman, Alison Rodger, Mike Cohen, and Pietro Vernazza announce results last summer.
Photo courtesy Prevention Access Campaign

Bruce Richman, the CEO of the Prevention Access Campaign and one of the first proponents of U=U, told A&U, “PARTNER2 went deep to clear up any lingering doubts about the risk from anal sex between men since participants in previous studies were mostly heterosexual-identified. PARTNER2 provided additional, unequivocal support to the [U=U] movement. PARTNER2 has helped bolster the movement tremendously. The endorsements in JAMA (the Journal of the American Medical Association) and quotes from Dr. Alison Rodger at AIDS2018 and in the press release unequivocally confirm that the risk is zero. This gives us the support we need to counter anyone who continues to cling to the stigmatizing notion that there is still statistical risk.”

Asked whether the HIV-negative partner in a serodiscordant relationship should take PrEP as a precaution, Richman said, “We absolutely don’t recommend PrEP for the HIV-negative partner. It’s not medically necessary when the HIV-positive partner is undetectable and it’s a waste of resources. Some HIV-negative partners choose to use it for added emotional security and agency, even though it’s not needed to prevent HIV.”

Richman concluded, “PARTNER2 is an extraordinary example of researchers who went above and beyond conducting the ground-breaking research, they also partnered with Prevention Access Campaign and U=U to make sure it was communicated properly to the people they intended to help. The U=U movement has flourished and is changing lives worldwide because of these unique collaborations between scientists and community.”

Professor Alison Rodger from University College London, and lead author on the PARTNER2 study, explained: “PARTNER2 data provides robust evidence for gay men that the risk of HIV transmission with suppressive ART is zero.”

Dr. Michael Brady, Medical Director at Terrence Higgins Trust, said, “It is impossible to overstate the importance of these findings. The PARTNER study has given us the confidence to say, without doubt, that people living with HIV who are on effective treatment cannot pass the virus on to their sexual partners. This has incredible impact on the lives of people living with HIV and is a powerful message to address HIV-related stigma.”

Simon Collins, an HIV positive treatment activist at HIV i-Base, London said, “PARTNER2 has met the community demand from gay men to have accurate data about our health. There is no evidence that HIV transmission can occur when viral load is undetectable. Our data support the international U=U awareness campaign.”

The PARTNER2 study was funded by the National Institute of Health Research UK. Other funding came from ViiV Healthcare, Gilead Sciences, Augustinus Fonden and A.P. Møller Fonden. The study is coordinated cooperatively between CHIP, Rigshospitalet, University of Copenhagen, and University College London.

For more information on the Prevention Access Campaign, check out

Hank Trout, Editor at Large, edited Drummer, Malebox, and Folsom magazines in the early 1980s. A long-term survivor of HIV/AIDS (diagnosed in 1989), he is a forty-year resident of San Francisco, where he lives with his fiancé Rick. Follow him on Twitter @HankTroutWriter.