title: Effect of Influenza Vaccination of Children on Infection Rate in Hutterite Communities: Follow-Up Study of a Randomized Trial.
abstract: BACKGROUND
  An earlier cluster randomized controlled trial (RCT) of Hutterite colonies had shown that if more than 80% of children and adolescents were immunized with influenza vaccine there was a statistically significant reduction in laboratory-confirmed influenza among all unimmunized community members. We assessed the impact of this intervention for two additional influenza seasonal periods.
  
  
  METHODS
  Follow-up data for two influenza seasonal periods of a cluster randomized trial involving 1053 Canadian children and adolescents aged 36 months to 15 years in Season 2 and 1014 in Season 3 who received the study vaccine, and 2805 community members in Season 2 and 2840 in Season 3 who did not receive the study vaccine. Follow-up for Season 2 began November 18, 2009 and ended April 25, 2010 while Season 3 extended from December 6, 2010 and ended May 27, 2011. Children were randomly assigned in a blinded manner according to community membership to receive either inactivated trivalent influenza vaccine or hepatitis A. The primary outcome was confirmed influenza A and B infection using RT-PCR assay. Due to the outbreak of 2009 H1N1 pandemic, data in Season 2 were excluded for analysis.
  
  
  RESULTS
  For an analysis of the combined Season 1 and Season 3 data, among non-recipients (i.e., participants who did not receive study vaccines), 66 of the 2794 (2.4%) participants in the influenza vaccine colonies and 121 of the 2301 (5.3%) participants in the hepatitis A colonies had influenza confirmed by RT-PCR, for a protective effectiveness of 60% (95% CI, 6% to 83%; P = 0.04); among all study participants (i.e., including both those who received study vaccine and those who did not), 125 of the 3806 (3.3%) in the influenza vaccine colonies and 239 of the 3243 (7.4%) in the hepatitis A colonies had influenza confirmed by RT-PCR, for a protective effectiveness of 63% (95% CI, 5% to 85%; P = 0.04).
  
  
  CONCLUSIONS
  Immunizing children and adolescents with inactivated influenza vaccine can offer a protective effect among unimmunized community members for influenza A and B together when considered over multiple years of seasonal influenza.
  
  
  BACKGROUND
  Clinicaltrials.gov NCT00877396.
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Biao
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Russell
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Lorraine
authors.initials: L
authors.lastname: Moss
authors.affiliation: Department of Microbiology and Infectious Diseases and Provincial Laboratory for Public Health, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Kevin
authors.initials: K
authors.lastname: Fonseca
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.|Michael G. De- Groote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada.|Department of Mathematics and Statistics, McMaster University, Hamilton, Ontario, Canada.
authors.forename: David J D
authors.initials: DJ
authors.lastname: Earn
authors.affiliation: Departments of Medicine, Medical Microbiology and Pharmacology, and Therapeutics, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Fred
authors.initials: F
authors.lastname: Aoki
authors.affiliation: Saskatchewan Disease Control Laboratory, Regina, Saskatchewan, Canada.
authors.forename: Gregory
authors.initials: G
authors.lastname: Horsman
authors.affiliation: Cadham Provincial Laboratory, Department of Medical Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Paul Van
authors.initials: PV
authors.lastname: Caeseele
authors.affiliation: Saskatchewan Health, Prince Albert Parkland Health Region, Prince Albert, Saskatchewan, Canada.
authors.forename: Khami
authors.initials: K
authors.lastname: Chokani
authors.affiliation: Saskatchewan Health, Five Hills Health Region, Moose Jaw, Saskatchewan, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Vooght
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Canada.
authors.forename: Lorne
authors.initials: L
authors.lastname: Babiuk
authors.affiliation: St Jude Children's Research Hospital and WHO Collaborating Center, Memphis, Tennessee, United States of America.
authors.forename: Richard
authors.initials: R
authors.lastname: Webby
authors.affiliation: Department of Microbiology and Infectious Diseases and Provincial Laboratory for Public Health, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Walter
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.|Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.|Michael G. De- Groote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada.|Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Loeb
mesh_terms: D000293:Adolescent; D002170:Canada; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D016896:Treatment Outcome
chemical_list: D007252:Influenza Vaccines