* To assess the safety of FluMist vaccination Rates of medically attended events in FluMist recipients, including serious adverse events (SAEs), anaphylaxis , urticaria, asthma, wheezing, pre-specified grouped diagnoses, and rare events potentially related to wild-type influenza, will be compared to rates in multiple non-randomized control groups.
* To assess the safety of annual FluMist re-vaccination \[Rates of MAEs in the subset of children who receive FluMist in ≥2 consecutive years will be compared to rates in first-time vaccinees during the same season.\]
* To assess the safety of FluMist vaccination in children previously vaccinated with trivalent inactivated influenza vaccine (TIV) \[Rates of MAEs in the subset of children who received one or more prior TIV vaccinations will be compared to rates in children who did not receive prior TIV.\]
