Alison Rodger discusses PARTNER2 study findings during a press conference at AIDS 2018 in Amsterdam. (Credit: Kenyon Farrow)
When British researcher Alison Rodger finished her presentation at the 22nd International AIDS Conference (AIDS 2018) in Amsterdam, the Netherlands, on July 25, she was met with an eruption of cheers and sustained applause -- an unusual reaction during a scientific data-sharing session. But this was no typical presentation: The findings she presented, that HIV-positive men who have sex with men (MSM) who were virally suppressed had zero risk of transmitting HIV to their partners, provided the most definitive conclusion yet that antiretroviral treatment is an extremely powerful tool in preventing HIV transmission -- and that the concept of U=U (undetectable equals untransmittable) can be applied just as reliably to gay men as to heterosexuals.
Rodger et al's research was a follow-up to the 2011 breakthrough PARTNER study, which primarily focused on heterosexual couples and was not as sufficiently powered for anal sex, a more efficient route of HIV transmission than penile-vaginal sex. This new study, called PARTNER2, followed a new cohort of 779 gay, male, serodiscordant couples from 14 European countries.
In the four-year (2014 to April 2018) observational study results presented at AIDS 2018, the researchers assessed 783 couples who contributed 1,596 couple-years of follow up (CYFU) including 76,991 individual acts of condom-free sex. The couples had sex an average of three to four times per month, with a median average of 43 sex acts per year. Every six to 12 months, both partners completed questionnaires about their sexual behavior; the HIV-negative partner received an HIV test; and the HIV-positive partner received a viral load test. CYFU data consisted of the time between HIV tests in which the couples had condomless sex with each other; the HIV-negative partner reported no use of pre- or post-exposure prophylaxis; and the HIV-positive partner had maintained a viral load below 200 copies/mL throughout the prior 12 months.
During the course of PARTNER2, 15 men acquired HIV. Using phylogenetic sequencing, researchers compared the newly acquired viruses of those men to the virus of their primary partner. They found zero linked infections, which means that each newly diagnosed person contracted HIV from a non-primary sexual partner who did not participate in the study. Thirty-seven percent of the enrolled couples reported having sex with an outside partner.
Researchers extrapolated the data to determine that it would take at least 419 years for there to be even the possibility of a transmission between serodiscordant MSM couples when the partner living with HIV is virally suppressed.
The PARTNER2 results yielded an equivalent level of confidence for gay men as it had for heterosexual couples in the original PARTNER study, also referred to as PARTNER1. Taken together, the findings affirm that there is no risk of HIV transmission when a person's HIV viral load is suppressed on treatment.
"It is clear through the PARTNER clinical trials that the chance that people who are virally suppressed can transmit HIV is zero. Undetectable does equal untransmittable," Rodger declared.
Carl Dieffenbach, Ph.D., director of the Division of AIDS at the National Institutes of Health, reinforced this message. "This update helps wrap up the [U=U] issue and adds to the data set, which will help reduce self-stigma for people living with HIV while also improving adherence," he told TheBodyPRO.
Dieffenbach added that the PARTNER2 results should help ensure no further pushback from health care providers who had been hesitant to affirm U=U with their gay patients. "The data clearly states an HIV virally suppressed gay man could have been having anal sex every day since the year 1600 and still would not have transmitted the virus," he said.
As the PARTNER2 results became public, the immediate response from the gay community was overwhelmingly positive.
"It's magical," said Daniel Driffin, M.P.H., the cofounder of THRIVE SS in Atlanta, Georgia, who attended AIDS 2018. "To know that people living with HIV can take treatment to prevent HIV is great. We still have to continue the efforts to get key populations -- especially black people in the U.S., gay and bisexual men, and trans women."
After Rodger completed her presentation of the PARTNER2 data, Bruce Richman, founder and executive director of the Prevention Access Campaign (and the creative mind behind the "U=U" campaign), stepped up to one of the microphones set up to facilitate audience questions in the large conference auditorium. "There are many providers that are still not accepting this message," Richman said. "They try to focus on [how] the risk is not zero scientifically; or they focus on [how] their patients aren't going to be adherent, and they won't know that they're detectable; or they say there's a rise of STIs [sexually transmitted infections] already, so they don't want to share this with their patients. We get every single kind of excuse. What would you say to clinicians -- or any other information provider -- who is withholding this information from people with HIV?"
Rodger didn't hesitate. "I think the time for excuses are over," she replied. "I think it's very, very clear that the risk is zero."
The packed room of attendees -- an international gathering of health care providers, researchers, non-clinical health workers, advocates, and community leaders -- began applauding again even before she had finished her answer.