title: H1N1 and seasonal influenza vaccine safety in the vaccine safety datalink project.
abstract: BACKGROUND
  The emergence of pandemic H1N1 influenza virus in early 2009 prompted the rapid licensure and use of H1N1 monovalent inactivated (MIV) and live, attenuated (LAMV) vaccines separate from seasonal trivalent inactivated (TIV) and live, attenuated (LAIV) influenza vaccines. A robust influenza immunization program in the U.S. requires ongoing monitoring of potential adverse events associated with vaccination.
  
  
  OBJECTIVE
  To prospectively conduct safety monitoring of H1N1 and seasonal influenza vaccines during the 2009-2010 season.
  
  
  METHODS
  The Vaccine Safety Datalink (VSD) Project monitors ∼9.2 million members in eight U.S. medical care organizations. Electronic data on vaccines and pre-specified adverse events were updated and analyzed weekly for signal detection from November 2009 to April 2010 using either a self-controlled design or a current versus historical comparison. Statistical signals were further evaluated using alternative approaches to identify temporal clusters and to control for time-varying confounders.
  
  
  RESULTS
  As of May 1, 2010, a total of 1,345,663 MIV, 267,715 LAMV, 2,741,150 TIV, and 157,838 LAIV doses were administered in VSD. No significant associations were noted during sequential analyses for Guillain-Barré syndrome, most other neurologic outcomes, and allergic and cardiac events. For MIV, a statistical signal was observed for Bell's palsy for adults aged ≥25 years on March 31, 2010, using the self-controlled approach. Subsequent analyses revealed no significant temporal cluster. Case-centered logistic regression adjusting for seasonality demonstrated an OR for Bell's palsy of 1.26 (95% CI=0.97, 1.63).
  
  
  CONCLUSIONS
  No major safety problems following H1N1 or seasonal influenza vaccines were detected in the 2009-2010 season in weekly sequential analyses. Seasonality likely contributed to the Bell's palsy signal following MIV. Prospective safety monitoring followed by rigorous signal refinement is critical to inform decision-making by regulatory and public health agencies.
authors.affiliation: Center for Child Health Care Studies, Department of Population Medicine, Children's Hospital Boston, Boston, Massachusetts, USA. grace_lee@hphc.org
authors.forename: Grace M
authors.initials: GM
authors.lastname: Lee
authors.forename: Sharon K
authors.initials: SK
authors.lastname: Greene
authors.forename: Eric S
authors.initials: ES
authors.lastname: Weintraub
authors.forename: James
authors.initials: J
authors.lastname: Baggs
authors.forename: Martin
authors.initials: M
authors.lastname: Kulldorff
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Fireman
authors.forename: Roger
authors.initials: R
authors.lastname: Baxter
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Jacobsen
authors.forename: Stephanie
authors.initials: S
authors.lastname: Irving
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Daley
authors.forename: Ruihua
authors.initials: R
authors.lastname: Yin
authors.forename: Allison
authors.initials: A
authors.lastname: Naleway
authors.forename: James D
authors.initials: JD
authors.lastname: Nordin
authors.forename: Lingling
authors.initials: L
authors.lastname: Li
authors.forename: Natalie
authors.initials: N
authors.lastname: McCarthy
authors.forename: Claudia
authors.initials: C
authors.lastname: Vellozzi
authors.forename: Frank
authors.initials: F
authors.lastname: Destefano
authors.forename: Tracy A
authors.initials: TA
authors.lastname: Lieu
mesh_terms: D000293:Adolescent; D000328:Adult; D016907:Adverse Drug Reaction Reporting Systems / Q000706:statistics & numerical data*; D000368:Aged; D020330:Bell Palsy / Q000453:epidemiology / Q000209:etiology; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000009:adverse effects*; D007251:Influenza, Human / Q000517:prevention & control*; D016015:Logistic Models; D008875:Middle Aged; D011446:Prospective Studies; D014481:United States; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines