Trial organizers would become more selective as they recruit participants, he said, "to make sure that we don't have people who have underlying immunity to the vector in question."
Both experts stressed that trial participants should always do their best to prevent exposure to HIV and not assume that an experimental vaccine gives them added protection.
"The counseling that people in trials get is really very thorough," Johnston said, "and yet I think that as trial participants, many people really do come away with the perception that they are being given a product that might protect them."
Safe behaviors -- especially condom use -- remain the surest way to prevent infection with HIV, whether you are in a trial or not, Johnston said. "To protect yourself, you really need to assume that the vaccine won't work, and then keep on protecting yourself in every way possible."
In the meantime, an estimated 39 million people remain infected with HIV worldwide, and the hope for a safe, effective vaccine delivered by a viral vector remains high, she said.
"The viral vector is really a very good idea -- it's still one of the best ideas that's out there," Johnston said. "I don't think the failure of one candidate from one company should signal the end of this as a concept."
Find out more about the fight against HIV/AIDS at amfAR.
SOURCES: Anthony Fauci, M.D., director, U.S. National Institute of Allergy and Infectious Diseases, Bethesda, Md.; Rowena Johnston, Ph.D., vice president, research, Foundation for AIDS Research, New York City; Nov. 7, 2007, statement, Merck & Co.
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