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Table 4 Vaccination histories in cases and control subjects, unadjusted and adjusted Odds Ratios, and estimates of effectiveness of pneumococcal vaccination against invasive pneumococcal disease according to influenza and noninfluenza periods.

From: Effectiveness of the 23-valent polysaccharide pneumococcal vaccine against invasive pneumococcal disease in people 60 years or older

    Unadjusted analysis Adjusted analysis
Type of infection No. of subjects No. (%) of vaccinated ORa (95% CI) Effectiveness of vaccination % (95% CI) ORb (95% CI) Effectiveness of vaccination % (95% CI)
Within influenza period (January-April)      (c)  
   Case patients 50 17 (34.0) 0.30 (0.12-0.73) 70% (27-88) 0.27 (0.08-0.85) 73% (15-92)
   Control subjects 100 55 (55.0) p = 0.008   p = 0.025  
Within non-influenza period (May-December)      (d)  
   Case patients 38 17 (44.7) 0.38 (0.16-0.92) 62% (8-84) 0.37 (0.15-0.92) 63% (8-85)
   Control subjects 76 49 (64.5) p = 0.032   p = 0.033  
  1. NOTE: OR, odds ratio of vaccination versus no vaccination in cases and controls; CI, confidence interval.
  2. aMantel-Haenszel matched Odds Ratio.
  3. bMatched, adjusted Odds Ratio by conditional logistic regression model.
  4. c Adjusted for age, chronic heart disease and influenza vaccine in the prior Autumn.
  5. d Adjusted for age and diabetes mellitus.