Two studies testing whether the drug Truvada (emtricitabine and tenofovir disoproxil fumarate) can prevent HIV infections in a real-world setting made their prime-time debuts this week at the Conference on Retroviruses and Opportunistic Infections in Seattle, Washington.

Both were a resounding success, boasting an 86 percent reduction in new HIV infections among volunteers using Truvada.

Truvada is an HIV medication FDA-approved to prevent the spread of HIV when it’s used as pre-exposure prophylaxis, or PrEP.

But the really big news is that researchers got the same results whether the men involved took Truvada once a day (as it’s typically prescribed) or “as needed” before and after risky sex.

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The first trial, called IPERGAY, included 400 men who have high-risk sex with other men in France and Canada. Volunteers were randomly assigned to take Truvada or placebo pills.

The men took two pills between two and 24 hours before sex, and a third and fourth pill 24 and 48 hours later. Because the men reported having sex frequently, they took Truvada an average of four days a week “as needed.”

There were two new HIV infections among men taking Truvada, and 14 new infections among those taking the placebo pills. Men in the trial taking Truvada lowered their risk of HIV infection by 86 percent.

The second trial, called PROUD, recruited 545 gay and bisexual men in the United Kingdom who admitted to having had recent unprotected sex. Half were assigned to begin taking Truvada every day right away, while half were assigned to receive Truvada after one year.

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In the group that started Truvada right away, three men contracted HIV. However, in the group that delayed Truvada, there were 19 new HIV infections. That's a risk reduction of 86 percent for the first group.

“These results are extremely exciting and show PrEP is highly effective at preventing HIV infection in the real world,” said Sheena McCormack, a professor of clinical epidemiology at University College London and chief investigator of the PROUD study. “These results show there is a need for PrEP, and offer hope of reversing the epidemic among men who have sex with men.”

Experts hope these results will remove some of the stigma surrounding Truvada and encourage more men to talk to their doctors about using PrEP.

They caution these results can’t be expanded to include opposite-sex couples, since the risk of infection during sex is different based on the type of sex partners have.  

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