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WASHINGTON (Reuters) - AIDS vaccine researchers are worried about the future of their field after learning an experimental HIV vaccine not only does not work, but just might make recipients more susceptible to infection with the AIDS virus.
They are worried about their volunteers and the future of AIDS vaccines in general. And they are worried because they cannot understand how a vaccine would make a person more vulnerable.
Researchers from Merck & Co. (MRK.N), which makes the vaccine, and the National Institute of Allergy and Infectious Diseases, which is helping develop it, said on Wednesday they believe a type of common cold virus used as the basis of the vaccine may somehow have made their volunteers more susceptible to HIV.
They are meeting this week in Seattle to hash through the data and figure out what happened.
This is what they know: Out of 1,500 people vaccinated, 82 became infected with the AIDS virus. Of these, 49 got the vaccine and 33 got a placebo shot.
While they are counseling volunteers that they may have raised their own risk of becoming infected, they are also trying to figure out what happened.
"The data are disappointing and puzzling but we don't have definitive answers," Dr. Lawrence Corey of Fred Hutchinson Cancer Research Center in Seattle, who was organizing the trial, told reporters.
Only one woman in the trial became infected with HIV. The rest were men having sex with other men, and it was the men who started out with the highest immune response to the adenovirus 5 common cold bug used to make the vaccine who were the most likely to become infected with the AIDS virus.
But the infected men were also less likely to have been circumcised -- circumcision can also prevent HIV infection -- and may have engaged in more risky behavior. So did the vaccine actually do something, or were the results a fluke?
"I don't think we really do know," Dr. Keith Gottesdiener of Merck Research Laboratories told Reuters.
Nearly 30 potential AIDS vaccines are being tested in people around the world.
"It is very important for the future of the field," said Margaret Johnston, director of the AIDS vaccine research program at the NIAID.
"It makes us rethink some of the candidates that are in trial," said Dr. Seth Berkley, president of the International AIDS Vaccine Initiative.
Even vaccine advocates are calling it a setback.
"These data are deeply disappointing and troubling, and raise more questions than answers for the field of AIDS vaccine," said AIDS Vaccine Advocacy Coalition executive director Mitchell Warren.
"This setback should not and can not diminish our commitment to developing an effective HIV vaccine," said NIAID director Dr. Anthony Fauci. "Every day, another 12,000 people become infected with HIV, most of whom live in resource-poor countries," he added.
The researchers agree the finding could at the very least scare people off from taking part in AIDS vaccine trials. And because HIV only infects people, having human volunteers is key to finding a way to prevent an infection that has killed 25 million people and affects 40 million more.
"That is why we are being completely transparent, as open as possible," Fauci said in a recent interview.
Berkley agreed. "I am only worried if there is a lot of buzz, misinformation around," he said.
But the fact that vaccine volunteers even became infected drives home the need for a vaccine, said Berkley. All the volunteers were counseled about ways to avoid HIV infection, and given condoms. "If those behavioral change interventions worked, we wouldn't need a vaccine," Berkley said.
"People will get infected despite the best counseling possible."
Reporting by Maggie Fox, editing by Jackie Frank