title: A postlicensure evaluation of the safety of Ann Arbor strain live attenuated influenza vaccine in children 24-59 months of age.
abstract: BACKGROUND
  In the United States, live attenuated influenza vaccine (LAIV) was initially approved for use in individuals aged 5-49 years in 2003, which was extended to individuals aged 2-49 years in 2007. At that time, a postlicensure commitment was made to describe the safety of LAIV within a cohort of eligible children aged 2-5 years.
  
  
  METHODS
  A prospective observational postmarketing study was conducted to evaluate the safety of LAIV. Rates of medically attended events (MAEs) and serious adverse events (SAEs) in eligible children aged 24-59 months receiving LAIV as part of routine care from October 2007 to March 2010 were compared with rates in a within-cohort self-control, as well as matched unvaccinated and matched trivalent inactivated influenza vaccine (TIV)-vaccinated controls. Children with asthma and other high-risk medical conditions before vaccination were excluded. All MAEs and SAEs through 42 days postvaccination and all hospitalizations and deaths through 6 months postvaccination were analyzed. Statistical significance was declared without multiplicity adjustment.
  
  
  RESULTS
  A total of 28,226 unique LAIV recipients were matched with similar numbers of TIV-vaccinated and unvaccinated children. Of 4696 MAE incidence rate comparisons, 83 (1.8%) were statistically significantly higher and 221 (4.7%) were statistically significantly lower in LAIV recipients versus controls. No pattern of MAE rate differences suggested a safety signal with LAIV. Asthma/wheezing MAEs were not statistically increased in LAIV recipients. No anaphylaxis events occurred within 3 days postvaccination. Rates of SAEs were similar between LAIV and control groups.
  
  
  CONCLUSIONS
  Results of this postlicensure evaluation of LAIV safety in US children are consistent with preapproval clinical studies and Vaccine Adverse Event Reporting System reports, both of which demonstrated no significant increase in asthma/wheezing events or other adverse outcomes among eligible children aged 24-59 months who received LAIV.
authors: MedImmune, LLC, One MedImmune Way, Gaithersburg, MD 20878, USA. Seth.Toback@gilead.com
authors: Seth L
authors: SL
authors: Toback
authors: Christopher S
authors: CS
authors: Ambrose
authors: Abigail
authors: A
authors: Eaton
authors: John
authors: J
authors: Hansen
authors: Laurie
authors: L
authors: Aukes
authors: Ned
authors: N
authors: Lewis
authors: Xionghua
authors: X
authors: Wu
authors: Roger
authors: R
authors: Baxter
mesh_terms: D002675:Child, Preschool; D064420:Drug-Related Side Effects and Adverse Reactions / Q000276:immunology; D005260:Female; D006801:Humans; D007252:Influenza Vaccines / Q000009:adverse effects* / Q000276:immunology; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control; D008297:Male; D011446:Prospective Studies; D014481:United States; D014611:Vaccination / Q000009:adverse effects; D014613:Vaccines, Attenuated / Q000009:adverse effects / Q000276:immunology
chemical_list: D007252:Influenza Vaccines; D014613:Vaccines, Attenuated