PARTNER 2 study results announced
The chance of any HIV-positive person with an undetectable viral load transmitting the virus to a sexual partner is scientifically equivalent to zero, researchers confirmed at the 22nd International AIDS Conference (AIDS 2018) in Amsterdam today.
Final results from the PARTNER study were presented this morning at a press conference on the opening day of AIDS 2018. Results originally announced in 2014 from the first phase, PARTNER 1, already indicated that “Undetectable equals Untransmittable” (U=U). However, the statistical certainty of this result was not quite as convincing in the case of gay men, or for anal sex, as it was for vaginal sex.
Results from PARTNER 2, the second phase, which only recruited gay couples, were presented today.
The results indicate, in the words of the researchers, “A precise rate of within-couple transmission of zero” for gay men as well as for heterosexuals.
The PARTNER study recruited HIV serodiscordant couples (one partner positive, one negative) at 75 clinical sites in 14 European countries. They tested the HIV-negative partners every six to 12 months for HIV, and tested viral load in the HIV-positive partners. Both partners also completed behavioural surveys. In cases of HIV infection in the negative partners, their HIV was genetically analysed to see if it came from their regular partner.
The study found no transmissions between gay couples where the HIV-positive partner had a viral load under 200 copies/ml – even though there were nearly 77,000 acts of condomless sex between them.
Why PARTNER matters
It is fitting that the results of PARTNER 2 appear on the tenth anniversary of an impassioned debate at the Mexico City International AIDS Conference in 2008 on the validity of the Swiss Statement, which was the first published document to say that, under defined circumstances, people with HIV who have fully suppressed viral loads due to treatment cannot transmit HIV.
At the time it was said that due to lack of viral load monitoring in anything but high-income countries, this fact – even if true – would have little relevance to most people with HIV.
There was also concern that telling people with HIV that they were not infectious if virally suppressed would be counter-productive because it would discourage safer sex. The more important message to give to people, some experts said, was that they should take every dose of their therapy.
The U=U (Undetectable equals Untransmittable) campaign was founded as a reaction to these positions.
The thinking behind U=U is that telling people they are not infectious if virally suppressed was a message of hope, and something earnestly desired by many people with HIV. It would help to combat the stigma against them, and their own self-stigma. By providing a powerful incentive to take treatment it could also have a positive impact on public health, as well as on individuals.
The Swiss doctors who issued the original 2008 statement apologised at the time that stating that people “do not” transmit HIV under the circumstances above was too definite, and that they had only meant to indicate that the likelihood of transmission was reduced.
But what PARTNER tells us is that they were right all along. People who are virally suppressed do not transmit HIV.
It was widely assumed at the time that sexually transmitted infections (STIs) might make people infectious even when they normally had an undetectable viral load.
But PARTNER tells us that STI infections have no impact on HIV infectiousness in people who are fully suppressed.
And it was thought that because HIV is transmitted more easily via anal than vaginal sex, the results might not hold for gay men.
But PARTNER 2 now tells us that U=U holds just as strongly for gay men (and for anal sex) as for heterosexuals. Read more via AIDSmap