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Table 2 Summary Relative Illness Ratio (sRIR), lower and upper 95% confidence intervals (CI), and between-estimates heterogeneity (as measured by the I2 statistics) for A(H1N1), A(H1N1)pdm2009, A(H3N2) and B influenza virus within each age group. The Global Influenza B Study, 1999-2014

From: Distribution of influenza virus types by age using case-based global surveillance data from twenty-nine countries, 1999-2014

Influenza virus sRIR lower CI (a) upper CI (a) I2
Young children (0-4 years)
 A(H1N1) 3.57 3.00 4.14 97.5%
 A(H1N1)pdm2009 2.28 2.10 2.46 97.8%
 A(H3N2) 3.30 2.95 3.64 98.2%
 B 2.93 2.68 3.19 97.5%
Older children (5-17 years)
 A(H1N1) 1.36 1.19 1.54 95.2%
 A(H1N1)pdm2009 1.23 1.02 1.45 99.5%
 A(H3N2) 1.04 0.93 1.14 97.2%
 B 1.69 1.53 1.85 98.4%
Young adults (18-39 years)
 A(H1N1) 0.84 0.72 0.96 97.1%
 A(H1N1)pdm2009 0.94 0.87 1.01 97.5%
 A(H3N2) 0.73 0.68 0.78 96.0%
 B 0.65 0.59 0.71 98.1%
Older adults (40-64 years)
 A(H1N1) 0.49 0.41 0.57 95.2%
 A(H1N1)pdm2009 0.62 0.55 0.69 98.7%
 A(H3N2) 0.59 0.55 0.63 93.5%
 B 0.41 0.37 0.45 96.6%
Elderly (65+ years)
 A(H1N1) 0.16 0.12 0.20 73.9%
 A(H1N1)pdm2009 0.27 0.24 0.31 94.7%
 A(H3N2) 0.74 0.66 0.83 95.2%
 B 0.38 0.33 0.43 92.4%
  1. (a)Because of the between-estimates heterogeneity being above 50%, the reported 95% CI very likely underestimate the real uncertainty in the data, and should be considered with caution.