Table 1.

Factors relating to the differences in SARS-CoV-2 antibody titres

	Age		p-value	Sex		p-value	N Ab		p-value
	Low (≤ 45 years)	High (> 45 years)		Men	Women		Negative	Positive
	n = 324	n = 312		n = 151	n = 485		n = 617	n = 19
Age, years	35.6 ± 7.8	54.1 ± 6.7	–	46.9 ± 13.4	44.0 ± 11.1	0.007	44.8 ± 11.8	40.4 ± 9.6	0.103
Men, n (%)	68 (21)	83 (27)	0.058	151 (100)	0 (0)	–	148 (24)	3 (16)	0.580
Log (S Ab) after 1 month of vaccination	3.11 ± 0.36	3.00 ± 0.35	< 0.001	3.00 ± 0.33	3.08 ± 0.36	0.029	3.04 ± 0.33	3.76 ± 0.55	< 0.001
Log (S Ab) after 7 months of vaccination	2.77 ± 0.39	2.65 ± 0.43	< 0.001	2.63 ± 0.41	2.74 ± 0.42	0.004	2.69 ± 0.37	3.64 ± 0.65	< 0.001
Delta log (S Ab)	− 0.34 ± 0.33	− 0.35 ± 0.36	0.638	− 0.37 ± 0.37	− 0.34 ± 0.34	0.257	− 0.35 ± 0.30	− 0.13 ± 1.03	0.004
N Ab positive after 7 months of vaccination, n (%)	12 (4)	7 (2)	0.198	3 (2)	16 (3)	0.289	0 (0)	19 (100)	–

Data are mean ± standard deviation or the numbers (percent)

SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; N Ab, nucleocapsid protein antibody; S Ab, spike protein antibody

Antibody titres for spike protein are represented as logarithmic values [log (S Ab)]

Delta log (S Ab) represents changes in logarithmic values of S Ab from 1 to 7 months after vaccination