title: Superinfection following smallpox vaccination (Vaccinia), United States: surveillance January 2003 through January 2004.
abstract: BACKGROUND
  Superinfection is an adverse event following smallpox vaccination. The clinical presentation is similar to that of a large normal vaccine reaction or "robust take," and the frequency is unknown.
  
  
  METHODS
  We retrospectively reviewed all reported severe local reactions consistent with superinfection among United States civilian smallpox vaccinees from January 2003 through January 2004. We applied a standard case definition and estimated the frequency of superinfection following smallpox vaccination.
  
  
  RESULTS
  We identified 48 reported cases for further review among 39,350 [corrected] smallpox vaccinees. Two (4%) of the 48 reported cases met the case definition for superinfection; neither of the patients had a pathogenic organism isolated from their infection site. Both were treated with antibiotics and resolved their infection. Of the 46 cases determined not to be superinfection, 41 (89%) were temporally consistent with a large normal vaccine reaction. Thirty (75%) of 40 reported case patients for whom data were available received antibiotic therapy.
  
  
  CONCLUSIONS
  Superinfection following smallpox vaccination is rare. Most of the reported superinfection cases were probably large normal smallpox vaccine reactions. Educating providers about the normal response to smallpox vaccine may decrease the overdiagnosis of superinfection and the unnecessary use of antimicrobials.
authors.affiliation: National Immunization Program, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. bno1@cdc.gov
authors.forename: Claudia
authors.initials: C
authors.lastname: Vellozzi
authors.forename: Francisco
authors.initials: F
authors.lastname: Averhoff
authors.forename: J Michael
authors.initials: JM
authors.lastname: Lane
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Wen
authors.forename: Anne C
authors.initials: AC
authors.lastname: Moore
authors.forename: Scott
authors.initials: S
authors.lastname: Santibanez
authors.forename: Andrew
authors.initials: A
authors.lastname: Kroger
authors.forename: La Mar
authors.initials: LM
authors.lastname: Hasbrouck
authors.forename: Allison
authors.initials: A
authors.lastname: Kennedy
authors.forename: Christine G
authors.initials: CG
authors.lastname: Casey
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D012189:Retrospective Studies; D015163:Superinfection / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology; D014615:Vaccinia / Q000453:epidemiology*