title: Epidemiological characteristics of varicella from 2000 to 2008 and the impact of nationwide immunization in Taiwan.
abstract: BACKGROUND
  Varicella has an important impact on public health. Starting in 2004 in Taiwan, nationwide free varicella vaccinations were given to 1-year-old children.
  
  
  METHODS
  Our study investigated the epidemiological characteristics of varicella from 2000 to 2008, and assessed the change of varicella epidemiology after the mass varicella immunization. ICD-9-CM codes related to varicella or chickenpox (052, 052.1, 052.2, 052.7, 052.8, 052.9) were analyzed for all young people under 20 years of age through the National Health Insurance database of Taiwan from 2000 to 2008.
  
  
  RESULTS
  Case numbers of varicella or chickenpox significantly declined after the nationwide immunization in 2004. Winter, particularly January, was the epidemic season of varicella. We found a significant post-vaccination decrease in incidence among preschool children, especially 3 to 6 year-old children-- the peak incidence was 66 per thousand for 4 and 5 year-old children before the nationwide immunization (2000 to 2003), and the peak incidence was 23 per thousand for 6 year-old children in 2008 (p < 0.001). Varicella-related hospitalization also significantly decreased in children younger than 6 years after the nationwide immunization.
  
  
  CONCLUSIONS
  The varicella annual incidence and varicella-related hospitalization markedly declined in preschool children after nationwide varicella immunization in 2004.
authors.affiliation: Department of Pediatrics, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan. lychang@ntu.edu.tw
authors.forename: Luan-Yin
authors.initials: LY
authors.lastname: Chang
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Huang
authors.forename: I-Shou
authors.initials: IS
authors.lastname: Chang
authors.forename: Fang-Yu
authors.initials: FY
authors.lastname: Tsai
mesh_terms: D000293:Adolescent; D002644:Chickenpox / Q000453:epidemiology* / Q000517:prevention & control*; D019433:Chickenpox Vaccine / Q000008:administration & dosage* / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007114:Immunization / Q000706:statistics & numerical data*; D015994:Incidence; D007223:Infant; D008297:Male; D013624:Taiwan / Q000453:epidemiology; D055815:Young Adult
chemical_list: D019433:Chickenpox Vaccine