Safety and Immunogenicity of a Live Attenuated H7N9 Influenza Virus Vaccine in Healthy Adults

Inclusion Criteria: * Adult males and non-pregnant females between 18 years and 49 years of age, inclusive. Children will not be recruited or enrolled in this study because they are not in the apparent risk group, and for safety considerations and because of the need for isolation. * General good health, without significant medical illness, physical examination findings, or significant laboratory abnormalities as determined by the investigator * Agree to storage of blood specimens for future research * Available for the duration of the trial * Willingness to participate in the study as evidenced by signing the informed consent document * Female participants of child-bearing potential must agree to use effective birth control methods for the duration of the study (for example, pharmacologic contraceptives including oral, parenteral, and transcutaneous delivery; condoms with spermicide; diaphragm with spermicide; intrauterine device; abstinence from heterosexual intercourse; surgical sterilization). All female participants will be considered being of child-bearing potential except those who have undergone hysterectomy and those in whom menopause occurred at least 1 year prior to the study. Exclusion Criteria: * Pregnancy, as determined by a positive human choriogonadotropin (beta-HCG) test * Currently breastfeeding * Evidence of clinically significant neurologic, cardiac, pulmonary, hepatic, rheumatologic, autoimmune, or renal disease by history, physical examination, and/or laboratory studies including urine testing. Alanine aminotransferase (ALT) levels greater than two times the upper normal limit will be exclusionary at baseline, prior to vaccination. * Behavioral or cognitive impairment or psychiatric disease that in the opinion of the investigator affects the ability of the participant to understand and cooperate with the study protocol * Previous enrollment in an H7 influenza vaccine trial or in any study of an avian influenza vaccine * Seropositive to the H7N9 influenza A virus (serum HAI titer greater than 1:8) * Positive urine drug toxicology test indicating narcotic use/dependency * Have medical, occupational, or family problems as a result of alcohol or illicit drug use during the past 12 months * Other condition that in the opinion of the investigator would jeopardize the safety or rights of a participant in the trial or would render the participant unable to comply with the protocol * History of anaphylaxis * Allergy to oseltamivir as determined by participant report * Current diagnosis of asthma or reactive airway disease (within the past 2 years) * History of Guillain-Barré Syndrome * Positive ELISA and confirmatory Western blot tests for human immunodeficiency virus-1 (HIV-1) * Positive ELISA and confirmatory test (e.g., recombinant immunoblot assay) for hepatitis C virus (HCV) * Positive hepatitis B virus surface antigen (HBsAg) by ELISA * Known immunodeficiency syndrome * Use of corticosteroids (excluding topical preparations) or immunosuppressive drugs within 30 days prior to vaccination * Receipt of a live vaccine within 4 weeks or a killed vaccine within 2 weeks prior to study vaccination * History of asplenia * Receipt of blood or blood-derived products (including immunoglobulin) within 6 months prior to study vaccination * Current smoker unwilling to stop smoking for the duration of the study: * A current smoker includes anyone stating they currently smoke any amount of a tobacco product. * The decision to exclude a potential participant is determined by medical history and a clinician's clinical judgment based on the physical examination. * After admission to the unit, nicotine patches will be provided to current smokers who request them for the inpatient portion of the study. * Travel to the Southern Hemisphere within 14 days prior to study vaccination * Travel on a cruise ship within 14 days prior to study vaccination * Receipt of another investigational vaccine or drug within 30 days prior to study vaccination * Allergy to eggs or egg products