title: An outbreak of varicella among schoolchildren in Taipei.
abstract: BACKGROUND
  The reported cases with varicella have not decreased and outbreaks of varicella among vaccinated children continue to be reported 9 years after the public vaccination program in Taipei. We investigated an outbreak to determine varicella vaccine coverage and effectiveness.
  
  
  METHODS
  An outbreak occurred in an elementary school which located in southern Taipei from April 2007 through May 2007. A retrospect cohort study was performed by using a self-administered questionnaire for parents.
  
  
  RESULTS
  Ten out of sixteen varicella cases were vaccinated. Overall vaccine coverage was 71.2%. The common reasons for not receiving varicella vaccine were that varicella vaccine was unavailable because the student didn't live in Taipei (29.4%) or the children could not be vaccinated due to certain illnesses (23.5%). The sensitivity and specificity of self-reported vaccination status was 0.900 (95% CI: 0.864, 0.935) and 0.611 (95% CI: 0.514, 0.701).The vaccine effectiveness was 69.3%-100.0% against any disease severity of varicella. Overall vaccine effectiveness against moderate or severe varicella was 85.5%. Attending cram school was associated with the risk of developing the varicella illness (RR: 13.39; 95% CI: 5.38, 33.31). Unvaccinated students tended to show moderate to severe (>50 lesions) afflictions of the disease (RR: 4.17; 95% CI: 1.15, 15.14).
  
  
  CONCLUSIONS
  Because of the low vaccination coverage, varicella outbreaks continue to be reported in Taipei. Increasing vaccine coverage and second dose vaccination for increasing vaccine effectiveness may be considered.
authors.affiliation: Emergency Department of Taipei City Hospital, Ren-Ai Branch, Taiwan, ROC.
authors.forename: Chao-Chih
authors.initials: CC
authors.lastname: Lai
authors.forename: Szu-Ching
authors.initials: SC
authors.lastname: Chen
authors.forename: Donald Dah-Shyong
authors.initials: DD
authors.lastname: Jiang
mesh_terms: D002644:Chickenpox / Q000453:epidemiology* / Q000517:prevention & control; D019433:Chickenpox Vaccine / Q000008:administration & dosage* / Q000276:immunology; D002648:Child; D004196:Disease Outbreaks / Q000517:prevention & control; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012307:Risk Factors; D012574:Schools; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013624:Taiwan / Q000453:epidemiology; D014611:Vaccination / Q000706:statistics & numerical data*
chemical_list: D019433:Chickenpox Vaccine