A major new study has revealed that HIV positive men who are undergoing effective treatment do not pass HIV to their negative partners.

In fact, the HIV medication seems to prevent the transmission of HIV with or without condom usage. This was true in over 40,000 incidents of condomless sex.

The groundbreaking results were released at the International AIDS Conference in Amsterdam today.

Aidsmap first reported the PARTNER 2 findings.

“It remains the case that the most likely probability, by far, that an HIV-positive person with a viral load under 200 copies/ml can infect their partner is zero,” their statement read.

“We looked so hard for transmissions,” said Aidsmap researcher Alison Rodger. “And we didn’t find any.”

The PARTNER 2 study followed the first PARTNER study back in 2014 where primarily opposite-sex couples were examined. Researchers expanded the study to include a larger grouping of same-sex couples for the follow-up study.

The theory being tested was whether or not male couples who engaged in anal sex could transmit HIV more easily than through vaginal sex.

There were 14 countries involved in the PARTNER 2 study. In total, 635 gay couples were vetted, in addition to the 337 gay couples already recruited for the PARTNER 1 study.

In total, there were approximately 77,000 acts of condomless sex reported in the group. Not a single incident of HIV transmission was found when the HIV positive partner had a viral load under 200.

Another study called Opposites Attract further validated the findings of PARTNER 2.

NAM’s Executive Director, Matthew Hodson, said in a statement, ‘This is the moment when science trumps stigma. This is the moment when facts must conquer fear.”

Hodson added, ‘The knowledge that when we are undetectable we can’t pass the virus on to our sexual partners has the power to encourage people to test and to remain adherent to their treatment. Just as importantly it can have an impact on the way that people with HIV think about themselves, removing some of the stress and fear that many in our communities experience.”

“What the PARTNER 2 study does is prove once again that people who are on effective and successful treatment cannot pass on HIV to their partners,” said Ian Howley, Chief Executive of HERO – Health Equality and Rights Organisation.

“This should be reassuring to every gay and bisexual man who is HIV-undetectable that you are not a danger to anyone and no person should use your status as a way to reject you,” Howley added.

He then cautioned, “However, the results of the PARTNER 2 study will not wipe away the stigma those living with HIV receive overnight. We have to continue to push the message and help educate those who still don’t believe the science behind the U=U movement.”

The U=U movement (Undetectable = Untransmittable U=U) “offers freedom and hope…For many people living with HIV and their partners, U=U opens up social, sexual, and reproductive choices they never thought would be possible,” according to Prevention Access.