Pneumonia: Influenza vaccination reduced death and hospitalisation in elderly patients

Clinical bottom line (level 2a)

  1. Elderly patients who have influenza vaccine were less likely to die (NNT = 140 at unknown) , develop pneumonia (NNT = 150 at unknown) or be admitted to hospital (NNT = 254 at unknown) .
Gross et al: Annals of Internal Medicine 1995; 123: 518-527
Expires March 2003

The study

Systematic review of all cohort studies of
  • Patients: elderly patients
  • Intervention: influenza vaccine
  • Outcome: death


    • Articles found in ?English using MEDline, (search terms: influenza vaccine, vaccine efficacy, elderly, mortality, hospitalized and pneumonia ) and and searching bibliographies of retrieved articles

    Selection criteria: see above
    Appraisal criteria: not given
    Articles excluded if:
    • artificial challenge studies
    • studies that described only upper respiratory illness scores
    • epidemic in progress
    • no description of epidemic or vaccine strains


    20 cohort studies found (11 prospective) involving 24774 patients
    Studies were combined using a random effects model. No heterogeneity was noted between studies for hospitalisation or mortality, but was for pneumonia.

    The evidence

    Outcome Time to outcome CER OR
    (95% CI)    		 NNT
    (95% CI)
    death unknown 226/21726
    (1.04%)    		 0.32
    (0.24 to 0.44)     		142
    (127 to 172)
    hospitalisation unknown 148/18848
    (0.79%)    		 0.50
    (0.35 to 0.72)     		254
    (195 to 455)
    pneumonia weeks 244/18836
    (1.30%)    		 0.47
    (0.34 to 0.65)     		146
    (117 to 222)

    Comments

    1. Results consistent with the single RCT available.
    2. There was as great an effect when there was a strain of influenza prevalent that had undergone antigenic drift (although not shift) compared to stains that were the same as the vaccination.

    Citation

    1. Gross PA, Hermogenes AW, Sacks HS, et al: the efficacy of influenza vaccine in elderly persons: a meta-analysis and review of the literature. Annals of Internal Medicine 1995; 123: 518-527
    Search Terms: ?
    Contributor: Bob Phillips and Musab Hayatli and Chris Ball, November 1999
    Reviewer: Chris Del Mar

    Clinical Question.
    Patient elderly
    Intervention or Exposure influenza vaccine
    Outcome death, pneumonia, hospitalisation