The U.S. government already has several million doses of an earlier bird flu vaccine, but it was based on a virus sample taken from Vietnam in 2004.  The virus is believed to have mutated significantly since then.

Today U.S. Health and Human Services Secretary Leavitt said he had authorized the National Institutes of Health and the federal Centers for Disease Control and Prevention to begin working on a second vaccine for humans.  “In order to be prepared, we need to continue to develop new vaccines,” Leavitt said at an immunization conference in Atlanta.