title: High Vaccination Coverage among Children during Influenza A(H1N1)pdm09 as a Potential Factor of Herd Immunity.
abstract: The objective of this study was to identify factors related to the expansion of infection and prevention of influenza A(H1N1)pdm09. A retrospective non-randomized cohort study (from June 2009 to May 2010) on influenza A(H1N1)pdm09 was conducted in a sample of residents from Hiroshima Prefecture, Japan. The cumulative incidence of the influenza A(H1N1)pdm09 and the pandemic vaccine effectiveness (VE) were estimated. The response rate was 53.5% (178,669/333,892). Overall, the odds ratio of non-vaccinated group to vaccinated group for cumulative incidence of influenza A(H1N1)pdm09 was 2.18 (95% confidence interval (CI): 2.13-2.23) and the VE was 43.9% (CI: 42.8-44.9). The expansion of infection, indicating the power of transmission from infected person to susceptible person, was high in the 7-15 years age groups in each area. In conclusion, results from this survey suggested that schoolchildren-based vaccination rate participates in determining the level of herd immunity to influenza and children might be the drivers of influenza transmission. For future pandemic preparedness, vaccination of schoolchildren may help to prevent disease transmission during influenza outbreak.
authors.affiliation: Department of Epidemiology, Infectious Disease Control and Prevention, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan. d133416@hiroshima-u.ac.jp.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Matsuoka
authors.affiliation: Department of Epidemiology, Infectious Disease Control and Prevention, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan. kounu-satou@outlook.com.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Epidemiology, Infectious Disease Control and Prevention, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan. tomo-akita@hiroshima-u.ac.jp.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Akita
authors.affiliation: Hiroshima City Funairi Citizens Hospital, Hiroshima 730-0844, Japan. yanayana@ruby.ocn.ne.jp.
authors.forename: Jiturou
authors.initials: J
authors.lastname: Yanagida
authors.affiliation: Department of Infectious Diseases, Hiroshima University Hospital, Hiroshima 734-8551, Japan. ohge@hiroshima-u.ac.jp.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ohge
authors.affiliation: Hiroshima Prefectural Center for Disease Control and Prevention, Hiroshima 734-0007, Japan. ba_ramasa@yahoo.co.jp.
authors.forename: Masao
authors.initials: M
authors.lastname: Kuwabara
authors.affiliation: Department of Epidemiology, Infectious Disease Control and Prevention, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan. jun-tanaka@hiroshima-u.ac.jp.
authors.forename: Junko
authors.initials: J
authors.lastname: Tanaka
mesh_terms: D000328:Adult; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D032521:Immunity, Herd; D015994:Incidence; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D007564:Japan / Q000453:epidemiology; D008297:Male; D016017:Odds Ratio; D012189:Retrospective Studies; D014611:Vaccination / Q000706:statistics & numerical data*
chemical_list: D007252:Influenza Vaccines
keywords: Influenza A(H1N1)pdm09; expansion of infection; herd immunity; pandemic; vaccination