 Study hypothesis: Influenza A viruses are widely distributed in nature and infect a wide variety of birds and mammals. The direct transmission of avian influenza viruses from birds to humans has recently become a major health concern in Asia and other parts of the world, raising concern of a possible influenza pandemic in humans. This vaccine will evaluate the safety, infectivity and immunogenicity of Live Influenza A vaccine H9N2 6-2 AA ca reassortant AchickenHong KongG997 x AAnn Arbor660 ca, a cold-adapted, live attenuated virus vaccine administered intranasally for the protection of humans against pandemic influenza viruses of the H9N2 subtype. 