Antiretroviral drug greatly reduces HIV transmission risk, new study says

An antiretroviral drug used to treat HIV is also highly effective at preventing the virus’ transmission if taken while engaging in risky sexual activity, according to study results released this week. Researchers from University College London (UCL) and Public Health England found that Truvada, an antiretroviral drug already used to treat HIV, reduced the risk of transmitting the disease by 86 percent among men who have sex with men (MSM).

Drugs such as Truvada, when taken before HIV is transmitted in a practice called pre-exposure prophylaxis (PrEP), have been shown to reduce HIV infections among MSM in controlled experiments. But the researchers wanted to know if PrEP could have the same effect in a real-world situation, and whether it might alter sexual behavior.

Starting in 2012, researchers gave Truvada to 545 men recruited from 13 United Kingdom health clinics. All of the men had recently had sex with other men without using a condom, and reported that they were likely to do so again in the future. Some were given the drug immediately, and others took it after a year so that researchers could compare results.

In the first year of the study there were just three new HIV infections among the men who began taking Truvada immediately, and 19 in the group who deferred the treatment for a year, researchers found. They said the 86 percent decrease in transmission risk is the highest that has ever been reported in a PrEP study.

“These results are extremely exciting and show PrEP is highly effective at preventing HIV infection in the real world,” Sheena McCormack, a clinical epidemiology professor at UCL and the lead author of the study, said in a statement. Researchers presented their results on Tuesday at the Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle.

"These results show there is a need for PrEP, and offer hope of reversing the epidemic among men who have sex with men in this country,” McCormack said.

In another study presented at the same conference, MSM in France and Canada who took PrEP immediately before and after sex were also 86 percent less likely to get HIV, according to researchers from the University of Paris Diderot and Montreal University Health Center.

“These new results are a significant breakthrough in advancing efforts to provide effective HIV prevention options to men who have sex with men,” said Michel Sidibé, executive director of the United Nations AIDS agency UNAIDS, in a statement. “The results are timely and important and will advance global efforts to end the AIDS epidemic by 2030.”

The U.S. Centers for Disease Control and Prevention has said that as many as 275,000 uninfected gay men could benefit from PrEP, as could some 140,000 heterosexual couples in which one partner is HIV-infected.

In 2014, the CDC recommended that health care workers prescribe PrEP to healthy people who are at risk of getting HIV, whether they are having sex without condoms or using intravenous drugs.

More than 1.2 million people in the U.S. have HIV, and about 50,000 people are newly infected each year, according to the CDC.