highly significantP < 0.01
Differences were considered statistically significant with ∗ P < 0.05 and highly significant with ∗∗ P < 0.01 and ∗∗∗ P < 0.001.
Differences were considered statistically significant with ∗ P < 0.05 and highly significant with ∗∗ P < 0.01 and ∗∗∗ P < 0.001.
Incidence rate ratios (IRR) for serotype 22F demonstrate an increasing trend (IRR 2.38; 95% CI 0.99–5.74 for the period 2017–2018 vs. 2009, IRR 1.82; 95% CI 1.06–3.12 for 2017–2018 vs. 2010–2012, and IRR 1.88; 95% CI 1.13–3.11 for 2017–2018 vs. 2013–2016 ( Table 2 ).