Table 2.

Multivariable weighted Cox hazard models of the association between 2020/21 influenza vaccination and SARS-CoV-2 first positive test (N = 2561).

Variable	Level	Model 1		Model 21
		npHR (95% CI)	p-value	npHR (95% CI)	p-value
Influenza vaccine	No	Ref	–	Ref	–
	Yes	0.37 (0.22–0.62)	<0.001	0.17 (0.09–0.34)	<0.001
Sex	Male	Ref	–	Ref	–
	Female	0.79 (0.55–1.16)	0.23	0.76 (0.52–1.11)	0.15
Age, years	1-year increase	1.00 (0.99–1.01)	0.91	0.99 (0.98–1.00)	0.17
Nationality	Italian	Ref	–	Ref	–
	Immigrant	1.38 (0.69–2.75)	0.37	1.39 (0.70–2.74)	0.34
SARS-CoV-2 testing frequency	1-unit increase	0.98 (0.93–1.04)	0.48	1.09 (1.02–1.16)	0.013

CI = confidence interval; npHR = non-proportional hazard ratio.

¹Adjusted for the week of the last SARS-CoV-2 RT-PCR testing.