title: Clinical effectiveness of influenza vaccination in Manitoba.
abstract: OBJECTIVE
  To assess the clinical effectiveness of influenza vaccination in preventing influenza-associated hospitalization and death.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Noninstitutionalized persons aged 45 years or older living in Manitoba, on December 1, 1982, and December 1, 1985.
  
  
  METHODS
  Linked records of the Manitoba population registry, hospital-discharge abstracts, physician claims for ambulatory-patient visits and influenza vaccination, and vital statistics were used. A matched-set analysis estimated the clinical effectiveness of influenza vaccination in preventing hospital admissions and deaths from influenza-associated conditions during influenza A (H3N2) outbreak periods in 1982 to 1983 (12 weeks) and 1985 to 1986 (10 weeks). The analysis adjusted for hospital discharge and ambulatory care for high-risk conditions within the previous 15 months and 3 months, respectively.
  
  
  RESULTS
  Influenza vaccination prevented 32% to 39% of hospital admissions with pneumonia and influenza and 15% to 34% of admissions with all respiratory conditions. Vaccination was 43% to 65% effective in preventing hospital deaths with these conditions (all listed diagnoses) and 27% to 30% effective in preventing deaths from all causes.
  
  
  CONCLUSIONS
  Influenza vaccination has substantial clinical effectiveness in preventing hospital admission and death from influenza-associated conditions in noninstitutionalized individuals.
authors.affiliation: Department of Medicine, University of Virginia School of Medicine, Charlottesville.
authors.forename: D S
authors.initials: DS
authors.lastname: Fedson
authors.forename: A
authors.initials: A
authors.lastname: Wajda
authors.forename: J P
authors.initials: JP
authors.lastname: Nicol
authors.forename: G W
authors.initials: GW
authors.lastname: Hammond
authors.forename: D L
authors.initials: DL
authors.lastname: Kaiser
authors.forename: L L
authors.initials: LL
authors.lastname: Roos
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D004196:Disease Outbreaks / Q000517:prevention & control / Q000706:statistics & numerical data; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D009980:Influenza A virus; D007252:Influenza Vaccines / Q000008:administration & dosage; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D008350:Manitoba / Q000453:epidemiology; D008875:Middle Aged; D009017:Morbidity; D012307:Risk Factors
chemical_list: D007252:Influenza Vaccines