title: Influenza vaccination: reduction in hospitalizations and death rates among members of "Maccabi Healthcare Services" during the 2000-2001 influenza season.
abstract: BACKGROUND
  Upper respiratory tract illnesses have been associated with an increased risk of morbidity and mortality.
  
  
  OBJECTIVE
  To assess the influence of vaccination against influenza on the risk of hospitalization in internal medicine and geriatric wards, and the risk of death from all causes during the 2000-2001 influenza season.
  
  
  METHODS
  A historical cohort study was conducted using computerized general practitioner records on patients aged 65 years and above, members of "Maccabi Healthcare Services"--the second largest health maintenance organization in Israel with 1.6 million members. The patients were divided into high and low risk groups corresponding to coexisting conditions, and were studied. Administrative and clinical data were used to evaluate outcomes.
  
  
  RESULTS
  Of the 84,613 subjects in the cohort 42.8% were immunized. At baseline, vaccinated subjects were sicker and had higher rates of coexisting conditions than unvaccinated subjects. Vaccination against influenza was associated with a 30% reduction in hospitalization rates and 70% in mortality rates in the high risk group. The NNT (number needed to treat) measured to prevent one hospitalization was 53.2 (28.2 in the high risk group and 100.4 in the low risk group). When referring to length of hospitalization, one vaccine was needed to prevent 1 day of hospitalization among the high risk group. Analyses according to age and the presence or absence of major medical conditions at baseline revealed similar findings across all subgroups.
  
  
  CONCLUSIONS
  In the elderly, vaccination against influenza is associated with a reduction in both the total risk of hospitalization and in the risk of death from all causes during the influenza season. These findings compel the rationale to increase compliance with recommendations for annual influenza vaccination among the elderly.
authors.forename: Yonatan
authors.initials: Y
authors.lastname: Shapiro
authors.forename: Joshua
authors.initials: J
authors.lastname: Shemer
authors.forename: Anthony
authors.initials: A
authors.lastname: Heymann
authors.forename: Varda
authors.initials: V
authors.lastname: Shalev
authors.forename: Nitzan
authors.initials: N
authors.lastname: Maharshak
authors.forename: Gabriel
authors.initials: G
authors.lastname: Chodik
authors.forename: Manfred S
authors.initials: MS
authors.lastname: Green
authors.forename: Ehud
authors.initials: E
authors.lastname: Kokia
mesh_terms: D000368:Aged; D015331:Cohort Studies; D015897:Comorbidity; D016001:Confidence Intervals; D005260:Female; D005853:Geriatrics; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007252:Influenza Vaccines / Q000627:therapeutic use*; D007251:Influenza, Human / Q000401:mortality / Q000517:prevention & control*; D007557:Israel; D008297:Male; D016347:Medical Records Systems, Computerized
chemical_list: D007252:Influenza Vaccines