TIV-vaccinated and unvaccinated subjects were matched to LAIV recipients on region (Northern California, Hawaii, Colorado), birth date (within one year), sex, and prior healthcare utilization. Prior utilization was calculated based on the number of clinic visits

during the 180 days before vaccination and classified as low (≤1 visit) and high (>1 visit) for matching. In Northern California, subjects also were matched on their specific medical clinic, of which there were 48. MAEs occurring in study subjects were collected from outpatient clinics, emergency departments (ED), and hospital admissions via extraction of Selleck Selumetinib records from the KP utilization databases. An MAE was defined as a coded medical diagnosis made by a health care provider and associated with a medical encounter. One or more MAEs could be assigned for a single encounter. Consistent

with a prior study of LAIV safety conducted in KP [3], medical events that were hypothesized see more a priori as potentially related to vaccination based on the pathophysiology of wild-type influenza were grouped in 5 event categories as prespecified diagnoses of interest (PSDI), and included (1) acute respiratory tract events (ART), (2) acute gastrointestinal tract events (AGI), (3) asthma and wheezing events (AW), (4) systemic bacterial infections (SBI), and (5) rare diagnoses potentially related to wild-type influenza (WTI). Asthma and wheezing events were a subset of ART; AW events were followed for 180 days, in contrast to the 42-day surveillance for other PSDIs (Supplemental Table 1). PSDI events were analyzed individually and cumulatively by group. Individual chart reviews were performed for select outcomes of interest to confirm specific diagnoses. SAEs were defined as events that resulted in any of the following outcomes: death, inpatient hospitalization, persistent or significant disability or incapacity, congenital anomaly/birth defect (in the offspring of a subject) or any life-threatening event. SAEs were identified from 0 to 42 days postvaccination and were reported regardless

of the investigator’s assessment of the relationship to LAIV. Any else subsequent serious event that was considered to be related to LAIV was also reported as an SAE. Assessment of the relationship between an SAE and LAIV was conducted by KP staff and based upon the temporal relationship of the event to the administration of the vaccine, whether an alternative etiology could be identified, and biological plausibility. Pregnancy was assessed by obtaining any pregnancy-related MAE within 42 days of vaccination in any setting or any pregnancy-related MAE in the ED or hospital setting within 180 days of vaccination. Chart review was performed on any subject with a pregnancy-related visit to verify the pregnancy and obtain outcome information.