title: Seasonal influenza vaccine effectiveness among children, 2010-2012.
abstract: BACKGROUND
  The annual differences in the seasonal influenza vaccine and the circulating strains make it necessary to assess influenza vaccine effectiveness (VE) yearly. We assessed the effectiveness of the trivalent inactivated influenza vaccine for the 2010-2011 and 2011-2012 influenza seasons among children in Guangzhou, China.
  
  
  METHODS
  We conducted a 1:2 matched case-control study based on date of birth (±7 days), gender, and area of residence. The influenza cases from surveillance sites in Guangzhou were laboratory-confirmed during the 2010-2012 seasons. The controls were randomly selected from children aged 6-59 months in the Children's Expanded Programmed Immunization Administrative Computerized System. The influenza vaccination information for both cases and controls was retrieved from this system.
  
  
  RESULTS
  We analyzed the vaccination information for 1255 influenza cases and 2510 matched controls in 2 influenza seasons in Guangzhou, China. We found that the VE for vaccination during the 2010-2011 and 2011-2012 seasons of virus circulation was 73·2% (95% confidence interval (CI), 52·2-85·0%) and 52·9% (95% CI, 42·1-61·7%), respectively. The VE decreased from 68·9% (95% CI, 57·5-77·2%) in the period between January and March to 48·4% (95% CI, 33·8-59·7%) in the period between April and June.
  
  
  CONCLUSIONS
  This post-licensing study of VE found moderate protection against influenza for vaccinated children aged 6-59 months. Although the influenza vaccine strains for the 2010-2011 and the 2011-2012 seasons were the same, our study indicated that annual vaccination is recommended even for those who received the vaccine during the previous season.
authors: Guangzhou Center for Disease Control and Prevention, Guangzhou, China.
authors: Chuanxi
authors: C
authors: Fu
authors: Qing
authors: Q
authors: He
authors: Zhaotian
authors: Z
authors: Li
authors: Jianxiong
authors: J
authors: Xu
authors: Yongqian
authors: Y
authors: Li
authors: Jianyun
authors: J
authors: Lu
authors: Kuibiao
authors: K
authors: Li
authors: Qiongying
authors: Q
authors: Yang
authors: Zhiqiang
authors: Z
authors: Dong
authors: Xiangyi
authors: X
authors: Liu
authors: Sijun
authors: S
authors: Wen
authors: Wensui
authors: W
authors: Hu
authors: Danfeng
authors: D
authors: Zhang
authors: Jiayun
authors: J
authors: Lv
authors: Wei
authors: W
authors: Zhu
authors: Ming
authors: M
authors: Wang
mesh_terms: D016022:Case-Control Studies; D002675:Child, Preschool; D002681:China; D005260:Female; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology
chemical_list: D007252:Influenza Vaccines; D015164:Vaccines, Inactivated
keywords: Case-control studies; China; children; seasonal influenza; vaccine
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