U.S. Halts Largest HIV Vaccine Trial on Treatment Failure

The largest and most advanced study under way of a vaccine to prevent HIV infection was stopped by U.S. government researchers after an interim look at the data showed it was unlikely to help recipients.

The National Institute of Allergy and Infectious Diseases said it will no longer give the injection, a combination of a DNA-based vaccine to prime the immune system and a booster shot with a weakened virus carrying genetic material that expressed HIV antigens. The vaccine didn’t prevent HIV infection or reduce the amount of virus in those who became infected, the agency said in a statement.

The vaccine was developed by the agency’s Vaccine Research Center. Volunteers who received the active vaccination unexpectedly had higher rates of HIV than those given a placebo, though the difference wasn’t large enough to rule out a chance finding, the agency said. The researchers will follow those who participated in the trial, which started in 2009, to see if other differences develop.

“While today’s result is disappointing, we need to look at the bigger picture of AIDS vaccine science,” said Mitchell Warren, executive director of AVAC: Global Advocacy for AIDS Prevention. “It’s not the answer we hoped for, but the search doesn’t end here.”

Funding Efforts

It is critical to fund efforts to develop an HIV vaccine and other methods to prevent infections in order to help end the AIDS epidemic, Warren said in a statement. A number of approaches different from that used in the current trial, known as HVTN 505, are showing promise and more data from the failed study will help refine those efforts, he said.

Doctors currently prescribe potent HIV drugs such as Gilead Sciences Inc.’s Truvada to those without the disease to prevent infection. Taking the pill daily can reduce the risk of contracting HIV by 94 percent. Developing an immunization that permanently prevents infection, without lifelong, expensive pills, would be a breakthrough, researchers said.

The U.S. study involved 2,504 volunteers in 19 cities across the country who received three shots over an eight-week period. After seven months, there were 27 HIV infections among those who got the vaccine and 21 infections in those given a placebo. When including everyone who participated, even those who hadn’t been in the trial for 28 weeks, there were 41 HIV infections in those given the vaccine and 30 in those given the placebo.

Numerous HIV vaccine efforts, including one with a similar approach to the current trial, have failed to show a benefit. Researchers continue to hunt for an immunization that can prevent infection after the first partially successful HIV vaccine trial in Thailand in 2009. That study showed two inoculations that hadn’t worked on their own offered some patients protection when given in combination.

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