1060 same way, creating more targets for HIV. But McElrath’s preliminary work found no evidence for this scenario. Behavioral changes don’t seem to provide an explanation: Study co-chair Susan Buchbinder of the San Francisco Department of Public Health said risk behaviors had decreased across the board and more so in the high–Ad5-antibody group. Buchbinder said investigators still are sorting out many variables related to HIV transmission, including circumcision, coinfection with other sexually transmitted diseases, and genetic factors. One thing is clear: The monkey studies that suggested that the vaccine could thwart the AIDS virus, fueling much excitement, misled Merck researchers.“Mice lie, monkey sometimes lie, and humans never lie,” said Peggy

Johnston, head of NIH’s AIDS vaccine program.“Some monkeys have lied to us this time.” Other attendees stressed that Merck relied on a wimpy strain of the AIDS virus to “challenge” vaccinated monkeys and that challenges with stronger strains predicted that the vaccine would fail.