Table 3:

Univariable and multivariable analyses of influenza-related acute respiratory infection; risk difference and risk ratio in COPD patients with and without influenza vaccination (N=320).

	Univariable analysis			Multivariable analysis
	crude	95% CI	p-value	adjusted	95% CI	p-value
	Risk difference			Risk difference
Vaccine
No		Reference			Reference
Yes	0.08	- 0.03, 0.18	0.175	- 0.14	- 0.24, - 0.03	0.012
Severity†
Low		-			Reference
High		-		0.42	0.31, 0.53	<0.001
		Risk ratio			Risk ratio
Vaccine
No		Reference			Reference
Yes	1.19	0.92, 1.53	0.179	0.74‡	0.59, 0.94	0.015
Severity
Low		-			Reference
High		-		2.70	2.01, 3.64	<0.001

CI, confidence interval

^†Severity of COPD

^‡Vaccine effectiveness adjusted for severity of COPD is 26% [from (1- RRadjusted)×100%].