Table 1. Demographic and baseline characteristics of patients in each group.

F: ANOVA, χ²: chi-square test; P < 0.05 indicates statistical significance.

≧1: patient's lymphocyte count on admission ≧1 (10^9/L); <1: patient's lymphocyte count on admission <1 (10^9/L).

Underlying disease: these include cardiovascular disease, hypertension, diabetes, inflammatory bowel disease, chronic kidney disease, chronic obstructive pulmonary disease, immunocompromised status, and cancer.

Variables	Total (n = 338)	Group				Statistic	P
		Unvaccinated		Vaccinated
		≧1	<1	≧1	<1
		A (n =51)	B (n = 66)	C (n = 108)	D (n = 113)
Age (years), mean ± SD	67.12 ± 18.18	68.18 ± 21.68	71.94 ± 16.33	61.91 ± 18.36	68.82 ± 16.26	F = 5.072	0.002
Gender, n (%)						χ² = 5.179	0.159
Male	180 (53.25)	22 (43.14)	34 (51.52)	55 (50.93)	69 (61.06)
Female	158 (46.75)	29 (56.86)	32 (48.48)	53 (49.07)	44 (38.94)
Underlying disease, n (%)						χ² = 13.274	0.004
Yes	235 (69.53)	40 (78.43)	51 (77.27)	61 (56.48)	83 (73.45)
No	103 (30.47)	11 (21.57)	15 (22.73)	47 (43.52)	30 (26.55)