The government is getting ready to test a bird-flu vaccine as fears of a pandemic from the virus grows. UN officials have warned that if the Asian bird flu mutates it could cause an outbreak that would pose the "gravest possible danger." Some experts think such an event could kill millions of people. To protect the country, the government is storing two million doses of the vaccine and will test how it maintains its potency. Officials say the new vaccine was prepared in two different concentrations and is nearly ready to be shipped to the National Institute for Allergy and Infectious Diseases for clinical trials.