Table 2.

Odds ratios (OR) of influenza onset versus vaccination and other characteristics in Japanese subjects: multivariate logistic regression

Variable	OR (95% CI)	P value
2013/2014 season vaccination	0.756 (0.738–0.776)	< 0.001
2012/2013 season vaccination	1.051 (1.024–1.079)	< 0.001
Insured persons (vs. dependents)	1.009 (0.965–1.056)	0.685
Female (vs. Male)	0.960 (0.940–0.980)	< 0.001
Number of children aged 0 to 15 years in a family a	1.114 (1.100–1.128)	< 0.001
Before influenza season
High-risk condition	1.138 (1.110–1.167)	< 0.001
Number of outpatient visits
During office hours (per visit)	1.016 (1.014–1.018)	< 0.001
Outside office hours (per visit)	1.000 (0.987–1.013)	0.980
Emergency hospitalization	0.897 (0.658–1.224)	0.493
During influenza season
Preceding onset of influenza in family members	1.263 (1.234–1.294)	< 0.001

Influenza onset was classified using the ICD-10 J10, J11 codes for clinical influenza. Age effects were modeled using linear tail-restricted cubic spline functions with 5 knots based on percentiles

^a Number of other dependents aged 0 to 15 years covered by the same insurance number