title: Changes in patterns of hospitalized children with varicella and of associated varicella genotypes after introduction of varicella vaccine in Australia.
abstract: BACKGROUND
  Varicella in children, although usually mild, can cause hospitalization and rarely death. This study examined patterns of hospitalized children with varicella, and associated varicella genotypes, in 4 tertiary children's hospitals throughout Australia before and after varicella vaccine was introduced.
  
  
  METHODS
  We obtained coded data on discharge diagnoses from each hospital before (1999 to 2001) and after (2007 to 2010) varicella vaccine introduction in 2005, adding active surveillance to capture clinical features, complications and immunization history in the latter period. Varicella vesicles were swabbed, and genotyping of varicella strains was performed by real-time polymerase chain reaction amplification.
  
  
  RESULTS
  Overall, a 68% reduction in coded hospitalizations (varicella, 73.2% [P < 0.001]; zoster, 40% [P = 0.002]) occurred post-vaccine introduction. Of children with detailed clinical data (97 varicella and 18 zoster cases), 46 (40%) were immunocompromised. Only 6 of 32 (19%) age-eligible immunocompetent children were immunized. Complications, most commonly secondary skin infections (n = 25) and neurologic conditions (n = 14), occurred in 44% of children. There were no deaths; but 3 immunocompetent unimmunized children had severe multiple complications requiring intensive care. All strains genotyped were "wild-type" varicella, with Clade 1 (European origin) predominating.
  
  
  CONCLUSIONS
  After the introduction of varicella vaccine, coverage of greater than 80% at 2 years of age was achieved, with varicella hospitalizations reduced by almost 70%. Of hospitalized children age-eligible for varicella vaccine, 80% were unimmunized, including all cases requiring intensive care.
authors.affiliation: Vaccinology and Immunology Research Trials Unit, Women's and Children's Hospital, South Australia, Australia. helen.marshall@adelaide.edu.au
authors.forename: Helen S
authors.initials: HS
authors.lastname: Marshall
authors.forename: Peter
authors.initials: P
authors.lastname: McIntyre
authors.forename: Peter
authors.initials: P
authors.lastname: Richmond
authors.forename: Jim P
authors.initials: JP
authors.lastname: Buttery
authors.forename: Jenny A
authors.initials: JA
authors.lastname: Royle
authors.forename: Michael S
authors.initials: MS
authors.lastname: Gold
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wood
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Elliott
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Zurynski
authors.forename: Cheryl S
authors.initials: CS
authors.lastname: Toi
authors.forename: Dominic E
authors.initials: DE
authors.lastname: Dwyer
authors.forename: Robert
authors.initials: R
authors.lastname: Booy
mesh_terms: D000293:Adolescent; D001315:Australia / Q000453:epidemiology; D016009:Chi-Square Distribution; D002644:Chickenpox / Q000150:complications / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology*; D019433:Chickenpox Vaccine / Q000008:administration & dosage* / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006562:Herpes Zoster / Q000150:complications / Q000453:epidemiology / Q000821:virology; D014645:Herpesvirus 3, Human / Q000235:genetics / Q000302:isolation & purification*; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D008297:Male; D016133:Polymerase Chain Reaction; D011446:Prospective Studies
chemical_list: D019433:Chickenpox Vaccine