title: Single-dose varicella vaccine effectiveness in school settings in China.
abstract: BACKGROUND
  Varicella vaccine has been available in the private sector in China for a decade as a single-dose regimen, but varicella vaccine effectiveness (VE) has not been fully examined in school settings yet.
  
  
  METHODS
  A matched case-control study was carried out in elementary schools and daycares in Tai'an prefecture, Shandong province, China. Clinical diagnosis of varicella and breakthrough disease was used for this study. Four controls were randomly selected from classmates; two from classmates of the case and two from another class of the same grade without cases. Vaccination status, date of vaccination, and vaccine product received if vaccinated were collected from home and clinic immunization records. Vaccination status of all students in schools/daycares with varicella cases from home immunization records or parental recall was used to calculate vaccination coverage.
  
  
  RESULTS
  The overall varicella VE was 83.4% (95% confidence interval 71.4-90.3%). Receipt of varicella vaccine five years or more years before the outbreak was significantly associated with breakthrough varicella (odds ratio=4.7, P<0.001), while age at vaccination (<15 vs. ≥15 months) was not (odds ratio=1.5, P=0.62). Varicella vaccination coverage was 41% with substantial variation across schools (range of 0-93.8%).
  
  
  CONCLUSIONS
  Single-dose varicella vaccine is highly effective in school settings. Maintaining limited vaccination coverage might shift varicella disease burden to older individuals, who are more prone to develop severe outcomes if varicella occurs.
authors.affiliation: Chinese Center for Disease Control and Prevention, Beijing, PR China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.forename: Huili
authors.initials: H
authors.lastname: Yang
authors.forename: Keli
authors.initials: K
authors.lastname: Li
authors.forename: Aihua
authors.initials: A
authors.lastname: Zhang
authors.forename: Zijian
authors.initials: Z
authors.lastname: Feng
authors.forename: Jane F
authors.initials: JF
authors.lastname: Seward
authors.forename: Stephanie R
authors.initials: SR
authors.lastname: Bialek
authors.forename: Chengbin
authors.initials: C
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002644:Chickenpox / Q000453:epidemiology / Q000517:prevention & control*; D019433:Chickenpox Vaccine / Q000008:administration & dosage*; D002648:Child; D002681:China; D004196:Disease Outbreaks / Q000517:prevention & control; D005260:Female; D006801:Humans; D008297:Male; D012574:Schools; D014611:Vaccination / Q000706:statistics & numerical data*
chemical_list: D019433:Chickenpox Vaccine
keywords: Chickenpox; Vaccination coverage; Vaccine effectiveness