A Post-Licensure Evaluation of the Safety of Live Attenuated Influenza Vaccine In Individuals 5 to 49 Years of Age

Background:  Live attenuated influenza vaccine (LAIV) was approved for eligible children and adults 5 to 49 years of age in June 2003. A post-licensure commitment was made to describe LAIV safety among 60,000 unique recipients.

Objectives: Evaluate the safety of LAIV among individuals 5 to 49 years of age.

Methods: Individuals received LAIV as part of routine care from October 2003 through March 2008. Using the Kaiser Permanente database, rates of medically attended events (MAEs) in LAIV recipients were compared with rates in multiple nonrandomized controls: a self-control, matched unvaccinated controls, and matched TIV recipients. Matching was based on age, gender and prior healthcare utilization. All MAEs through 42 days postvaccination and all hospitalizations and deaths through 6 months postvaccination were analyzed. Statistical significance was assigned without multiplicity adjustment.

Results: A total of 63,061, 62,492, and 71,949 subjects received LAIV, TIV, and no vaccine, respectively. The only MAEs found to be statistically increased in comparison with all 3 control groups were breast lump/cyst and mastitis; both were deemed biologically implausible. No asthma/wheezing MAEs were statistically increased in LAIV recipients; 3 asthma/wheezing MAEs were decreased. No anaphylaxis events occurred within 3 days postvaccination. Serious adverse events (SAEs) within 42 days occurred in 107 subjects. Five SAEs were considered possibly or probably related: Bell’s palsy (n=3), nonspecific paroxysmal spell (n=1), and migraine/sinusitis (n=1). Nine deaths occurred within 180 days; all were considered unrelated to LAIV.

Conclusions: The results of the current post-licensure evaluation of LAIV safety in individuals 5 to 49 years of age are consistent with pre-approval clinical studies and reports to the US Vaccine Adverse Events Reporting System in the years following LAIV approval, both of which demonstrated no significant adverse outcomes among eligible individuals following receipt of LAIV.