A Post-Licensure Evaluation of the Safety of Live Attenuated Influenza Vaccine in U.S. Children 5-17 Years of Age

Background: Live attenuated influenza vaccine (LAIV) was initially approved in the U.S. for eligible children >5 years of age in June 2003. A post-licensure commitment was made to describe LAIV safety among 40,000 children.

Objectives: Evaluate the safety of LAIV among individuals 5-17 years of age

Methods: Eligible children received LAIV as part of routine care from October 2003 through March 2008. Using Kaiser Permanente databases, rates of medically attended events (MAEs) in LAIV recipients were compared with three nonrandomized control groups: a self-control, matched unvaccinated controls, and matched trivalent inactivated influenza vaccine (TIV) recipients. Children with high-risk disorders were excluded. MAEs were identified in the clinic, emergency department, and hospital. All MAEs through 42 days postvaccination and hospitalizations and deaths through 6 months postvaccination were analyzed. Statistical significance was assigned without multiplicity adjustment.

Results: 43,702 subjects 5-17 years were vaccinated with 53,369 doses of LAIV and matched with similar numbers of TIV-vaccinated and unvaccinated children. Approximately 9500 MAE incidence rate comparisons were performed, 341 of which yielded statistically significant differences: 191 were higher and 150 were lower in LAIV recipients vs controls. No asthma/wheezing MAEs were statistically increased in LAIV recipients. No anaphylaxis events occurred within 3 days postvaccination. Only 1 MAE, breast lump/cyst in subjects 9-17 years of age (n=7), was associated with a significant increase among LAIV recipients vs control groups. Serious adverse events (SAEs) within 42 days postvaccination occurred in 64 subjects. Two SAEs were considered possibly related: Bell’s palsy and nonspecific paroxysmal spell. Three deaths occurred within 180 days postvaccination; all were considered unrelated to LAIV.

Conclusions: This post-licensure study of children 5-17 years is consistent with pre-approval studies and VAERS reports, which demonstrate no significant increase in asthma/wheezing events or other adverse outcomes among eligible children who received LAIV. Sponsored by MedImmune, LLC.