December 6, 2010

Daily Drug Reduces Risk for HIV Infection

Photo of two men

A pill that's currently used to treat HIV infection can also greatly reduce the risk of acquiring HIV among at-risk men. The finding, from a large clinical trial, represents a major advance toward HIV prevention.

Each year more than 2.5 million people worldwide are diagnosed with HIV, the virus that causes AIDS. Although progress has been made in reducing the number of new infections, scientists continue to search for more effective strategies to block HIV's spread. Current prevention strategies rely on behavioral changes, such as condom use, abstinence or fewer sexual partners.

Some studies in animals and humans have hinted that the antiretroviral medications now used to treat HIV might also help to prevent new infections. To test this idea, a clinical trial was launched at 11 sites in South America, South Africa, Thailand and the United States. The trial was sponsored by NIH’s National Institute of Allergy and Infectious Diseases (NIAID), with additional funding from the Bill and Melinda Gates Foundation. The study enrolled nearly 2,500 men who have sex with men. All participants were at least 18 years old and HIV-negative at the time of enrollment.

The men were randomly assigned to receive either a daily tablet containing 2 common antiretroviral medications (emtricitabine and tenofovir) or a placebo pill. They were then evaluated each month for HIV infection. All received condoms, counseling about safe sex practices, and treatment for other sexually transmitted diseases. The average length of enrollment in the study was 1.2 years.

The results, reported in the November 23, 2010, online edition of the New England Journal of Medicine, showed that the drug reduced the risk of acquiring HIV infection by nearly 44%. Specifically, 36 HIV infections occurred among the 1,251 participants who received the antiretroviral therapy, compared to 64 HIV infections among the 1,248 people who received the placebo.

The treatment was most effective for those who stuck to the daily regimen. Participants who took the drug at least half of the time had about 50% fewer HIV infections. Those who took the drug on 90% or more days had nearly 73% fewer infections. The researchers note that their findings are potentially relevant only to men who have sex with men. Additional studies will examine how effective the strategy might be in other populations, such as women and heterosexual men.

"No single HIV prevention strategy is going to be effective for everyone," says NIAID Director Anthony S. Fauci. "Additional research is needed, but certainly this is an important finding that provides the basis for further investigating, developing and employing this prevention strategy, which has the potential to make a significant impact in the fight against HIV/AIDS."

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