title: The risk of Guillain-Barré syndrome associated with influenza A (H1N1) 2009 monovalent vaccine and 2009-2010 seasonal influenza vaccines: results from self-controlled analyses.
abstract: OBJECTIVE
  The Centers for Disease Control and Prevention Emerging Infections Program implemented active, population-based surveillance for Guillain-Barré syndrome (GBS) following H1N1 vaccines in 10 states/metropolitan areas. We report additional analyses of these data using self-controlled methods, which avoid potential confounding from person-level factors and co-morbidities.
  
  
  METHODS
  Surveillance officers identified GBS cases with symptom onset during October 2009-April 2010 and ascertained receipt of H1N1 vaccines. We calculated self-controlled relative risks by comparing the number of cases with onset during a risk interval 1-42 days after vaccination with cases with onset during fixed (days 43-84) or variable (days 43-end of study period) control intervals. We calculated attributable risks by applying statistically significant relative risks to an independent estimate of GBS incidence.
  
  
  RESULTS
  Fifty-nine GBS cases received H1N1 vaccine with or without seasonal vaccine. The relative risk was 2.1 (95%CI 1.2, 3.5) by the variable-window and 3.0 (95%CI 1.4, 6.4) by the fixed-window analyses. The corresponding attributable risks per million doses administered were 1.5 (95%CI 0.3, 3.4) and 2.8 (95%CI 0.6, 7.4).
  
  
  CONCLUSIONS
  These attributable risks are similar to those of some previous formulations of seasonal influenza vaccine (about one to two cases per million doses administered), suggesting a low risk of GBS following the H1N1 vaccine that is not clearly higher than that of seasonal influenza vaccines.
authors.affiliation: Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention (CDC), Atlanta, GA 30333, USA. jit1@cdc.gov
authors.forename: Jerome I
authors.initials: JI
authors.lastname: Tokars
authors.forename: Paige
authors.initials: P
authors.lastname: Lewis
authors.forename: Frank
authors.initials: F
authors.lastname: DeStefano
authors.forename: Matthew
authors.initials: M
authors.lastname: Wise
authors.forename: Melissa
authors.initials: M
authors.lastname: Viray
authors.forename: Oliver
authors.initials: O
authors.lastname: Morgan
authors.forename: Paul
authors.initials: P
authors.lastname: Gargiullo
authors.forename: Claudia
authors.initials: C
authors.lastname: Vellozzi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D020275:Guillain-Barre Syndrome / Q000453:epidemiology* / Q000209:etiology; 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; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D012306:Risk; D014481:United States; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines