Incidence of invasive pneumococcal disease in children with commercial insurance or Medicaid coverage in the United States before and after the introduction of 7- and 13-valent pneumococcal conjugate vaccines during 1998–2018

Table 4 Estimates from ITS analyses of monthly unspecified IPD episode incidence rates in commercially insured children aged < 18 years (1998–2018)

		All ages		Ages < 2		Ages 2–4		Ages 5–17
Period^a	IRR	IRR (95% CI)^b,^c	p-value	IRR (95% CI)^b,^c	p-value	IRR (95% CI)	p-value	IRR (95% CI)^b,^c	p-value
Pre-PCV7	Base Trend	1.022 (1.008; 1.036)	0.002**	1.013 (0.985; 1.043)	0.368	1.071 (1.016; 1.129)	0.011*	1.000 (0.949; 1.054)	0.994
Early PCV7	Change in Level	0.500 (0.333; 0.750)	0.001**	0.607 (0.318; 1.159)	0.13	0.232 (0.117; 0.461)	0.001***	0.735 (0.280; 1.932)	0.533
Early PCV7	Change in Trend	0.972 (0.958; 0.986)	0.001***	0.972 (0.943; 1.003)	0.076	0.933 (0.885; 0.983)	0.010*	1.000 (0.949; 1.054)	0.995
Late PCV7	Change in Level	1.123 (0.906; 1.391)	0.291	1.480 (1.036; 2.115)	0.031*	1.193 (0.877; 1.622)	0.262	0.720 (0.495; 1.047)	0.085
Late PCV7	Change in Trend	1.014 (1.006; 1.021)	0.001**	1.017 (1.006; 1.029)	0.003**	1.000 (0.990; 1.011)	0.943	1.017 (1.005; 1.030)	0.005**
Early PCV13	Change in Level	0.653 (0.522; 0.817)	0.001***	0.637 (0.476; 0.851)	0.002**	0.669 (0.364; 1.231)	0.197	0.653 (0.449; 0.951)	0.026*
Early PCV13	Change in Trend	0.986 (0.980; 0.993)	0.001***	0.988 (0.979; 0.997)	0.009**	0.994 (0.977; 1.012)	0.538	0.978 (0.965; 0.991)	0.001**
Late PCV13	Change in Level	1.141 (0.921; 1.415)	0.228	1.390 (1.065; 1.815)	0.016*	1.064 (0.692; 1.634)	0.778	0.964 (0.693; 1.340)	0.826
Late PCV13	Change in Trend	1.005 (0.998; 1.012)	0.17	1.001 (0.990; 1.011)	0.886	1.010 (0.991; 1.028)	0.312	1.006 (0.994; 1.018)	0.331

Abbreviations: CI Confidence internal, IPD Invasive pneumococcal disease, IRR Incidence rate ratio, ITS Interrupted time series, PCV Pneumococcal conjugate vaccine
Significance codes: ∗ p < 0.05; ∗ ∗ p < 0.01; ∗ ∗ ∗ p < 0.001. P-values less than 0.001 are shown as 0.001***
^aTime periods are defined as follows: Pre PCV7: 1998–1999; Early PCV7: 2001–2005; Late PCV7: 2006–2009; Early PCV13: 2011–2013; Late PCV13: 2014–2018. Years 2000 and 2010 are considered transition years and were excluded from the model
^bAll coefficients were obtained through a negative binomial model with a log link, controlling for seasonality using monthly indicators. IRRs represent the exponentiated regression coefficients and indicate a multiplicative change. Model intercepts are not shown
^cConfidence intervals have been adjusted for heteroscedasticity

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