This is an observational post-marketing study conducted in children and adults immunized with Q/LAIV as part of routine clinical practice at Kaiser Permanente Northern California (NCKP) sites.

Children and adults will be immunized with Q/LAIV as part of routine clinical practice at Kaiser Permanente Northern California (NCKP) sites. Using existing data on healthcare utilization, rates of medically attended events (MAEs) of interest will be evaluated in all eligible Q/LAIV recipients who are vaccinated in the Kaiser Permanente (KP) Northern California Health Care Plan during the 2013-2014 influenza season. Enrollment must include a minimum of 10,000 children 2 through 8 years of age; based on previous utilization of FluMist at NCKP, enrollment is expected to include approximately 80,000 children and adults 2 to 49 years of age.

Inclusion Criteria:

1. . Age 2 through 49 years at the time of vaccination (or index date for unvaccinated controls)
2. . Membership in the KP Health Care Plan for at least 12 months prior to vaccination/index date
3. . Continuous enrollment in KP Health Care Plan through 6 months following vaccination/index date.

Exclusion Criteria:

NONE

Children and adults 2 to 49 years of age vaccinated with Q/LAIV, TIV or no vaccine at Kaiser Permenente Northern California sites.