Immunogenicity and Safety Study of Inactivated Subunit H5N1 Influenza Vaccine in Prior Recipients of Live Attenuated H2N2, H6N1 and H9N2 Influenza Vaccines and in H5N1 and Live Attenuated Vaccine Naïve Individuals

Inclusion Criteria: * Adult males and non-pregnant females between 18 years and 60 years of age inclusive. * General good health, without significant medical illness, physical examination findings, or significant laboratory abnormalities as determined by the investigator. * Available for the duration of the trial. * Able to demonstrate understanding of key study concepts, study rationale, and study participation requirements by scoring greater than or equal to 70% on a written comprehension assessment in 3 or fewer attempts. * Willingness to participate in the study as evidenced by signing the informed consent document. * Willingness to allow storage and testing of laboratory samples for future research. * Received 2 doses of live attenuated H2N2, H6N1, or H9N2 vaccine in a prior trial (Cohort 1) or H2N2, H6N1 and H9N2 naïve (Cohort 2) * Willingness to forego seasonal influenza virus vaccination from 1 month before vaccination until 3 months after vaccination. * Female subjects of childbearing potential must agree to have used effective birth control methods beginning at least one month prior to vaccination, and continuing with 'per label/fully effective use' for the chosen method for duration of the study, from amongst these: * pharmacologic/hormonal contraceptives, including oral, parenteral, subcutaneous, and transcutaneous delivery; * condoms with spermicide; * diaphragm with spermicide; * intrauterine device; * absolute abstinence from heterosexual intercours…