title: Seasonal influenza vaccine effectiveness against medically attended influenza illness among children aged 6-59 months, October 2011-September 2012: A matched test-negative case-control study in Suzhou, China.
abstract: Seasonal influenza infections among young children in China lead to substantial numbers of hospitalizations and financial burden. This study assessed the seasonal influenza vaccine effectiveness (VE) against laboratory confirmed medically attended influenza illness among children in Suzhou, China, from October 2011-September 2012.
  
  
  
  We conducted a test-negative case-control study among children aged 6-59 months who sought care at Soochow University Affiliated Children's Hospital (SCH) from October 2011-September 2012. A case was defined as a child with influenza-like illness (ILI) or severe acute respiratory infection (SARI) with an influenza-positive nasopharyngeal swab by rRT-PCR. Controls were selected from children presenting with ILI or SARI without laboratory confirmed influenza. We conducted 1:1 matching by age and admission date. Vaccination status was verified from the citywide immunization system database. VE was calculated with conditional logistic regression: (1-OR)×100%.
  
  
  
  During the study period, 2634 children aged 6-59 months presented to SCH with ILI (1975) or SARI (659) and were tested for influenza. The vaccination records were available for 69% (1829; ILI: 1354, SARI: 475). Among those, 23% (427) tested positive for influenza, and were included as cases. Among influenza positive cases, the vaccination rates were 3.2% for SARI and 4.5% for ILI. Among controls, the vaccination rates were 13% for SARI, and 11% for ILI. The overall VE against lab-confirmed medically attended influenza virus infection was 67% (95% CI: 41-82). The VE for SARI was 75% (95% CI: 11-93) and for ILI was 64% (95% CI: 31-82).
  
  
  
  The seasonal influenza vaccine was effective against medically attended lab-confirmed influenza infection in children aged 6-59 months in Suzhou, China in the 2011-12 influenza season. Increasing seasonal influenza vaccination among young children in Suzhou may decrease medically attended influenza-associated ILI and SARI cases in this population.
authors.affiliation: Department of Epidemiology, School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Epidemiology, School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Suzhou Center for Disease Prevention and Control, Suzhou, China.
authors.forename: Liling
authors.initials: L
authors.lastname: Chen
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Greene
authors.affiliation: Suzhou University Affiliated Children's Hospital, Suzhou, China.
authors.forename: Yunfang
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Department of Epidemiology, School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China.
authors.forename: Yuejia
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Department of Epidemiology, School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Epidemiology, School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Zeng
authors.affiliation: Suzhou University Affiliated Children's Hospital, Suzhou, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Hua
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Suizan
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Song
authors.affiliation: Suzhou Center for Disease Prevention and Control, Suzhou, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Luan
authors.affiliation: Suzhou Center for Disease Prevention and Control, Suzhou, China. Electronic address: sz_zhangj@163.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Epidemiology, School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China. Electronic address: gmzhao@shmu.edu.cn.
authors.forename: Genming
authors.initials: G
authors.lastname: Zhao
mesh_terms: D016022:Case-Control Studies; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D008297:Male; D012621:Seasons; D018571:Sentinel Surveillance; D014611:Vaccination; D064166:Vaccine Potency
chemical_list: D007252:Influenza Vaccines
keywords: Children; China; Influenza; Test-negative case–control; Vaccine effectiveness