title: Increased risk of anaphylaxis following administration of 2009 AS03-adjuvanted monovalent pandemic A/H1N1 (H1N1pdm09) vaccine.
abstract: BACKGROUND
  Anaphylaxis after trivalent influenza vaccination is typically reported at a rate of <1 per million doses. In Quebec, Canada, anaphylaxis following administration of the monovalent AS03-adjuvanted H1N1pdm09 vaccine was reported through passive surveillance at a rate of 8 per million doses administered. This was 20 times higher than the reporting rate for non-adjuvanted trivalent vaccines administered during the six previous seasons. However, adequate estimation of the incidence of anaphylaxis is hindered by wide variations in definitions and diagnosis.
  
  
  METHODS
  Using the Brighton collaboration case definition of anaphylaxis, all cases with allergic symptoms (AS) reported to public health were reviewed to estimate the incidence of anaphylaxis following AS03-adjuvanted H1N1pdm09 vaccine.
  
  
  RESULTS
  Among 752 reports of allergic symptoms, 33 were initially reported as anaphylaxis of which 20/33 (60%) met the Brighton definition (19/20 with certainty levels 1 or 2). A total of 38 additional cases with onset within 1h of vaccination also met the Brighton definition of anaphylaxis (27 (71%) with certainty levels 1 or 2). The 58 cases meeting Brighton Level 1 or 2 criteria for anaphylaxis represent a 75% increase over the 33 passively reported and an incidence of 13 per million doses administered.
  
  
  CONCLUSIONS
  A substantial number of patients with early-onset allergic symptoms met the most specific levels of the Brighton case definition but were not reported as anaphylaxis. Based on this specific case definition, the incidence of anaphylaxis after AS03-adjuvanted H1N1pdm09 vaccine substantially exceeded that reported with seasonal influenza vaccines, a signal that warrants better understanding.
authors.affiliation: Centre hospitalier universitaire de Québec, Quebec City, Quebec, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Rouleau
authors.forename: Gaston
authors.initials: G
authors.lastname: De Serres
authors.forename: Jean Philippe
authors.initials: JP
authors.lastname: Drolet
authors.forename: Danuta M
authors.initials: DM
authors.lastname: Skowronski
authors.forename: Manale
authors.initials: M
authors.lastname: Ouakki
authors.forename: Eveline
authors.initials: E
authors.lastname: Toth
authors.forename: Monique
authors.initials: M
authors.lastname: Landry
authors.forename: Suzanne
authors.initials: S
authors.lastname: Ménard
authors.forename: Rémi
authors.initials: R
authors.lastname: Gagnon
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000009:adverse effects; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000707:Anaphylaxis / Q000139:chemically induced* / Q000453:epidemiology*; D002170:Canada; D002648:Child; D002675:Child, Preschool; D004338:Drug Combinations; D064420:Drug-Related Side Effects and Adverse Reactions / Q000453:epidemiology / Q000473:pathology; D005260:Female; D006801:Humans; D015994:Incidence; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000009:adverse effects*; D007251:Influenza, Human / Q000517:prevention & control / Q000821:virology; D008297:Male; D008875:Middle Aged; D011136:Polysorbates / Q000008:administration & dosage* / Q000009:adverse effects*; D011792:Quebec; D018570:Risk Assessment; D013185:Squalene / Q000008:administration & dosage* / Q000009:adverse effects*; D055815:Young Adult; D024502:alpha-Tocopherol / Q000008:administration & dosage* / Q000009:adverse effects*
chemical_list: D000276:Adjuvants, Immunologic; D004338:Drug Combinations; D007252:Influenza Vaccines; D011136:Polysorbates; D013185:Squalene; C550253:AS03 adjuvant; D024502:alpha-Tocopherol
keywords: Adverse effects; Anaphylaxis; Epidemiology; Influenza vaccines; Mass vaccination