Study to Evaluate the Effectiveness of FluMist Vaccination in a School-Based Intervention Program

Inclusion Criteria: * Healthy children enrolled in the target schools. * Written informed consent obtained from the child's parent(s) if they agree to participate. Exclusion Criteria: * History of severe hypersensitivity (anaphylactic response) to egg products or previous FluMist * FluMist is licensed exclusively for use in healthy individuals age 5-49 years. Therefore children for whom annual receipt of inactivated influenza vaccine for specific medical condition(s) is recommended will not be eligible. These conditions include: * Asthma, other chronic pulmonary diseases, kidney disease, metabolic disease, heart disease, or hemoglobinopathy * Immunosuppression of child * Severe immunosuppression of a household member * Pregnancy * Past history of Guillian-Barre Syndrome * Aspirin therapy within 1 month prior to FluMist or the anticipated use of aspirin containing products for one month after FluMist administration * Administration of any inactivated vaccine within 2 weeks or any live vaccine within 4 weeks prior to receipt of FluMist * Received anti-influenza medication in the past 48 hours * Fever in the past 72 hours * Moderate to severe nasal congestion (inability to breathe through the nose) or acute phase URI symptoms until the congestion has improved