Table 2

Incidence rate ratios (IRR) with 95% CIs by gender, age group and time period*

Risk factorIRR (95% CI)
Sex
 Male1 (baseline)
 Female0.82 (0.72 to 0.93)
Age group and period†
<1 year
 Prepandemic
 (October 2003 to March 2009)
0.77 (0.50 to 1.18)
 Pandemic wave 2
 (October 2009 to March 2010)
2.06 (1.25 to 3.39)
 Pandemic wave 3
 (October 2010 to March 2011)
5.51 (3.65 to 8.32)
 Postpandemic
 (October 2011 to March 2013)
1 (baseline)
 Universal paediatric influenza vaccination programme (October 2013 to March 2017)1.58 (1.05 to 2.37)
1 year
 Prepandemic0.82 (0.40 to 1.67)
 Pandemic wave 23.56 (1.69 to 7.48)
 Pandemic wave 35.61 (2.81 to 11.2)
 Postpandemic1 (baseline)
 Universal paediatric influenza vaccination programme2.71 (1.43 to 5.17)
2–4 years
 Prepandemic0.68 (0.38 to 1.21)
 Pandemic wave 22.80 (1.52 to 5.16)
 Pandemic wave 33.98 (2.26 to 7.03)
 Postpandemic1 (baseline)
 Universal paediatric influenza vaccination programme1.98 (1.18 to 3.31)
5–15 years
 Prepandemic0.44 (0.27 to 0.70)
 Pandemic wave 25.18 (3.40 to 7.89)
 Pandemic wave 33.90 (2.51 to 6.05)
 Postpandemic1 (baseline)
 Universal paediatric influenza vaccination programme1.45 (0.96 to 2.19)
  • *The models exclude two children with missing sex information.

  • †The IRRs by period are presented for each age group separately since the age group:time period effect modification term significantly improved the fit of the model and was therefore included.