title: Risk of anaphylaxis after vaccination in children and adults.
abstract: BACKGROUND
  Anaphylaxis is a potentially life-threatening allergic reaction. The risk of anaphylaxis after vaccination has not been well described in adults or with newer vaccines in children.
  
  
  OBJECTIVE
  We sought to estimate the incidence of anaphylaxis after vaccines and describe the demographic and clinical characteristics of confirmed cases of anaphylaxis.
  
  
  METHODS
  Using health care data from the Vaccine Safety Datalink, we determined rates of anaphylaxis after vaccination in children and adults. We first identified all patients with a vaccination record from January 2009 through December 2011 and used diagnostic and procedure codes to identify potential anaphylaxis cases. Medical records of potential cases were reviewed. Confirmed cases met the Brighton Collaboration definition for anaphylaxis and had to be determined to be vaccine triggered. We calculated the incidence of anaphylaxis after all vaccines combined and for selected individual vaccines.
  
  
  RESULTS
  We identified 33 confirmed vaccine-triggered anaphylaxis cases that occurred after 25,173,965 vaccine doses. The rate of anaphylaxis was 1.31 (95% CI, 0.90-1.84) per million vaccine doses. The incidence did not vary significantly by age, and there was a nonsignificant female predominance. Vaccine-specific rates included 1.35 (95% CI, 0.65-2.47) per million doses for inactivated trivalent influenza vaccine (10 cases, 7,434,628 doses given alone) and 1.83 (95% CI, 0.22-6.63) per million doses for inactivated monovalent influenza vaccine (2 cases, 1,090,279 doses given alone). The onset of symptoms among cases was within 30 minutes (8 cases), 30 to less than 120 minutes (8 cases), 2 to less than 4 hours (10 cases), 4 to 8 hours (2 cases), the next day (1 case), and not documented (4 cases).
  
  
  CONCLUSIONS
  Anaphylaxis after vaccination is rare in all age groups. Despite its rarity, anaphylaxis is a potentially life-threatening medical emergency that vaccine providers need to be prepared to treat.
authors.affiliation: Immunization Safety Office, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Ga. Electronic address: mmm2@cdc.gov.
authors.forename: Michael M
authors.initials: MM
authors.lastname: McNeil
authors.affiliation: Immunization Safety Office, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Ga.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Weintraub
authors.affiliation: Immunization Safety Office, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Ga.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Duffy
authors.affiliation: Immunization Safety Office, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Ga.
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Sukumaran
authors.affiliation: Southern California Kaiser Permanente, Pasadena, Calif.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Jacobsen
authors.affiliation: Kaiser Permanente Vaccine Study Center, Oakland, Calif.
authors.forename: Nicola P
authors.initials: NP
authors.lastname: Klein
authors.affiliation: Institute for Health Research, Kaiser Permanente, Denver, Colo.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Hambidge
authors.affiliation: Department of Population Medicine, Harvard Medical School and the Harvard Pilgrim Health Care Institute, Boston, Mass.
authors.forename: Grace M
authors.initials: GM
authors.lastname: Lee
authors.affiliation: Group Health Research Institute, Seattle, Wash.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Jackson
authors.affiliation: Center for Health Research, Kaiser Permanente Northwest, Portland, Ore.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Irving
authors.affiliation: Marshfield Clinic Research Foundation, Marshfield, Wis.
authors.forename: Jennifer P
authors.initials: JP
authors.lastname: King
authors.affiliation: HealthPartners Institute for Education and Research, Minneapolis, Minn.
authors.forename: Elyse O
authors.initials: EO
authors.lastname: Kharbanda
authors.affiliation: Kaiser Permanente Center for Health Research, and the Rollins School of Public Health, Emory University, Atlanta, Ga.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Bednarczyk
authors.affiliation: Immunization Safety Office, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Ga.
authors.forename: Frank
authors.initials: F
authors.lastname: DeStefano
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000707:Anaphylaxis / Q000453:epidemiology* / Q000209:etiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012306:Risk; D014611:Vaccination / Q000009:adverse effects*; D014612:Vaccines / Q000009:adverse effects; D055815:Young Adult
chemical_list: D014612:Vaccines
keywords: Anaphylaxis; immunization; vaccine safety