Just two of the 35 scientists surveyed said they were more optimistic about the prospects for an HIV vaccine than they were a year ago, while only four said they were more optimistic now than they were five years ago, the survey by Britain's Independent newspaper said.

The survey found that nearly two-thirds believed an HIV vaccine will not be developed within the next 10 years. Some of the scientists said it may take at least 20 more years of research.

Researchers said the direction of AIDS research needs to change after the failure last year of a promising prototype vaccine used as an animal model for more than a decade. AIDS researcher Robert Gallo told the newspaper the vaccine's failure is similar to the Challenger disaster that forced the space agency to ground its space shuttle fleet for years.