Table 1. Multivariable estimate of JE risk ratio for vaccine coverage year, controlling for seasonal periodicity using Poisson regression.

Variables	RR/β (95% CI of RR)	Std. Error	p-valuea
Vaccine year (Jul 01–Dec 06) at 2-month lag	0.391b (0.273, 0.560)	0.1838	<0.001
Non-vaccine year (Apr 97–Jun 01) at 2-month lag	1c	.	.
cos12	−0.288d	0.1420	0.043
cos6	−0.190d	0.1313	0.148
sin12	−0.500d	0.1297	<0.001
sin6	0.391d	0.1313	0.003
Intercept	0.398d	0.1142	<0.001

RR = risk ratio;

^aBased on Wald chi-square test;

^bRisk Ratio;

^cReference.

^dβ-value.

Akaike information criterion = 317.398, Adjusted Pseudo-R² = 0.278. cos12 and sin12 models annual periodicity; cos6 and sin6 models biannual periodicity. Pseudo- R² is based on 1 minus the deviance ratio between the full model vs. the Intercept only model adjusting for the number of explanatory terms in a model (1 – (Full model _DEV/Intercept only model _DEV) * ((n-1)/(n-k-1))), where n is the sample size and k is the number of explanatory terms.