The PARTNER study, published in The Lancet medical journal on Thursday, surveyed 782 gay couples across 14 European countries who were having regular unprotected anal sex between 2010 and 2017.
In each case one partner had HIV and was taking anti-retroviral pills, and one was free of the virus. None of the partners without HIV contracted it, despite 76,088 reports of unprotected intercourse.
The study's results show the drugs have lowered the virus to undetectable levels in the blood, which means HIV cannot be passed on via sexual intercourse.
"Our findings provide conclusive evidence that the risk of HIV transmission through anal sex when HIV viral load is suppressed is effectively zero," the paper stated.
"Among the 782 different gay couples followed for almost 1600 eligible couple-years of follow-up, which included more than 76,000 reports of condomless sex, we found zero cases of within-couple HIV transmission."
Medication taken by HIV suffers will not eliminate the virus but it will reduce it to undetectable levels, letting many with HIV live a long life.
In the early days after contracting HIV, prophylaxis medication can be taken and can often stop a person becoming infected.
Dr Michael Brady, medical director at HIV charity Terrence Higgins Trust told Business Insider:
"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."
Health experts have a bullish plan to end the spread of HIV in the US by 2030.
This article was originally published by Business Insider.
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