The World Health Organization (WHO), based in Geneva, will back large-scale clinical trials of two experimental HIV vaccines that failed earlier this year to win similar approval in the United States. In June, Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), chose not to support the complex and costly trials because "the science wasn't there to justify it." Each vaccine relies on stimulating an immune response to the surface protein gp120 on the virus thought to cause AIDS. Apparently, the international health organization looked at the same data Fauci did, from smaller trials in humans, and saw sufficient immune system improvement demonstrated to warrant further studies. "The World Health Organization, in contrast to the NIAID, has decided to go ahead and test these vaccines in efficacy trials and put their blessing on that," says Don Francis, the clinical scientist managing the trials for Genentech....