Table 3.

Cox proportional hazards survival analysis of the pre-Omicron period

	HR	95% CI	P value
Sex (Reference: male)
Female	0.59	0.34–1.01	0.056
Age (Reference: 18–29)
30–39	0.91	0.34–2.49	0.859
40–49	1.06	0.44–2.50	0.911
50–59	0.94	0.36–2.44	0.902
≥ 60	0.53	0.17–1.65	0.272
Job title (Reference: physicians)
Nurses	1.18	0.59–2.35	0.644
Technicians	0.35	0.09–1.32	0.120
Administrative	0.32	0.07–1.49	0.147
Other HCWs	0.61	0.23–1.61	0.321
Previous infections (Reference: no previous infections)
Before 1st vaccine dose	1.22	0.20–6.19	0.894
After 1st vaccine dose
Serological response (Reference: medium)
High	0.27	0.11–0.66	0.004
Low	1.03	0.42–2.52	0.947