title: Estimating influenza vaccine effectiveness using routine surveillance data among children aged 6-59 months for five consecutive influenza seasons.
abstract: OBJECTIVE
  We aimed to estimate the pooled vaccine effectiveness (VE) in children over five winters through data linkage of two existing surveillance systems.
  
  
  METHODS
  Five test-negative case-control studies were conducted from November to February during the 2004/2005 to 2008/2009 seasons. Sentinel physicians from the Viral Surveillance Network enrolled children aged 6-59 months with influenza-like illness to collect throat swabs. Through linking with a nationwide vaccination registry, we measured the VE with a logistic regression model adjusting for age, gender, and week of symptom onset. Both fixed-effects and random-effects models were used in the meta-analysis.
  
  
  RESULTS
  Four thousand four hundred and ninety-four subjects were included. The proportion of influenza test-positive subjects across the five seasons was 11.5% (132/1151), 7.2% (41/572), 23.9% (189/791), 6.6% (75/1135), and 11.2% (95/845), respectively. The pooled VE was 62% (95% confidence interval (CI) 48-83%) in both meta-analysis models. By age category, VE was 51% (95% CI 23-68%) for those aged 6-23 months and 75% (95% CI 60-84%) for those aged 24-59 months.
  
  
  CONCLUSIONS
  Influenza vaccination provided measurable protection against laboratory-confirmed influenza among children aged 6-59 months despite variations in the vaccine match during the 2004/2005 to 2008/2009 influenza seasons in Taiwan.
authors.affiliation: Centers for Disease Control, Ministry of Health and Welfare, Taipei 10050, Taiwan; Institute of Epidemiology and Preventive Medicine, National Taiwan University, Taipei, Taiwan; Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Wei-Ju
authors.initials: WJ
authors.lastname: Su
authors.affiliation: Research Center for Humanities and Social Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: Ta-Chien
authors.initials: TC
authors.lastname: Chan
authors.affiliation: The Taiwan Foundation for Poison Control, Taipei, Taiwan.
authors.forename: Pei-Hung
authors.initials: PH
authors.lastname: Chuang
authors.affiliation: Centers for Disease Control, Ministry of Health and Welfare, Taipei 10050, Taiwan.
authors.forename: Yu-Lun
authors.initials: YL
authors.lastname: Liu
authors.affiliation: Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Ping-Ing
authors.initials: PI
authors.lastname: Lee
authors.affiliation: Centers for Disease Control, Ministry of Health and Welfare, Taipei 10050, Taiwan. Electronic address: mtliu@cdc.gov.tw.
authors.forename: Ming-Tsan
authors.initials: MT
authors.lastname: Liu
authors.affiliation: Centers for Disease Control, Ministry of Health and Welfare, Taipei 10050, Taiwan; Institute of Health Care Administration, National Yang-Ming University, Taipei, Taiwan. Electronic address: jhchuang@cdc.gov.tw.
authors.forename: Jen-Hsiang
authors.initials: JH
authors.lastname: Chuang
mesh_terms: D016022:Case-Control Studies; D002675:Child, Preschool; D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D007223:Infant; D009980:Influenza A virus / Q000276:immunology; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D016015:Logistic Models; D008297:Male; D012621:Seasons; D013624:Taiwan / Q000453:epidemiology
chemical_list: D007252:Influenza Vaccines
keywords: Case–control studies; Influenza surveillance; Influenza vaccine effectiveness