title: Safety of the yellow Fever vaccine: a retrospective study.
abstract: BACKGROUND
  Yellow fever (YF) vaccine is considered safe; however, severe illness and death following vaccination have been reported.
  
  
  METHODS
  Vaccine Safety Datalink (VSD) and US Department of Defense (DoD) data were used to identify adverse reactions following YF vaccination. Within the VSD, YF-vaccine-exposed subjects were compared to age-, site-, and gender-matched unexposed subjects. YF-vaccine-exposed DoD subjects were studied using a risk-interval design. For both cohorts, ICD-9 codes were analyzed for allergic and local reactions, mild systemic reactions, and possible visceral and neurologic adverse events (AEs).
  
  
  RESULTS
  The VSD cohort received 47,159 doses from 1991 through 2006. The DoD cohort received 1.12 million doses from 1999 through 2007. Most subjects received other vaccines simultaneously. In the VSD cohort, rates of allergic, local, and mild systemic reactions were not statistically different between YF-vaccine-exposed and -unexposed subjects. In the DoD, there was an increased risk for outpatient allergic events in the period following vaccination with YF and other vaccines rate ratios [RR 3.85, 95% confidence interval (CI) 3.35-4.41] but with no increased risk for inpatient allergic reactions. In both cohorts, inpatient ICD-9 codes for visceral events were significantly less common following vaccination; inpatient codes for neurologic events were less common in the VSD YF-vaccine-exposed adult cohort, but did not differ between exposed and unexposed periods in the DoD. In the DoD, one fatal case of YF-vaccine-associated viscerotropic disease (YF-vaccine-AVD) was detected. The estimated death rate was 0.89 for 1,000,000 YF vaccine doses (95% CI 0.12-6.31/1,000,000 doses). No YF vaccine-associated deaths occurred in the VSD.
  
  
  CONCLUSIONS
  In these closed cohorts we did not detect increased risk for visceral or neurologic events following YF vaccination. The death rate following YF vaccine was consistent with previous reports. These data support current recommendations for use of YF vaccine in young healthy individuals. These data are inadequate to judge safety of YF vaccines in elderly patients.
authors.affiliation: HealthPartners Institute for Education and Research, Minneapolis, MN, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Nordin
authors.forename: Emily D
authors.initials: ED
authors.lastname: Parker
authors.forename: Gabriela
authors.initials: G
authors.lastname: Vazquez-Benitez
authors.forename: Elyse O
authors.initials: EO
authors.lastname: Kharbanda
authors.forename: Allison
authors.initials: A
authors.lastname: Naleway
authors.forename: S Michael
authors.initials: SM
authors.lastname: Marcy
authors.forename: Beth
authors.initials: B
authors.lastname: Molitor
authors.forename: Leslie
authors.initials: L
authors.lastname: Kuckler
authors.forename: James
authors.initials: J
authors.lastname: Baggs
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology; D014611:Vaccination / Q000592:standards*; D015004:Yellow Fever / Q000453:epidemiology / Q000517:prevention & control*; D022341:Yellow Fever Vaccine / Q000494:pharmacology*; D015005:Yellow fever virus / Q000276:immunology*; D055815:Young Adult
chemical_list: D022341:Yellow Fever Vaccine