Table 1.

Serological levels SARS-CoV-2 Immunoglobulin G (IgG), overall, and by strata of gender, age group, and IgG reactivity, before and after COVID-19 mRNA vaccination.

		Prevaccination	15 days postvaccination	90 days postvaccination	180 days postvaccination
	N (%)	T0 (× 101)	T1 (× 103)	T2 (× 103)	T3 (× 103)
IgG titers, AU/ml*	2968 (100)	6.8 [6.8, 6.8]	21.3 [13.3, 33.0]	3.2 [2.0, 5.1]	1.0 [0.64, 1.6]
Gender  Male  Female	667 (22.5) 2301 (77.5)	6.8 [6.8, 6.8] 6.8 [6.8, 6.8]	18.7 [11.7, 29.3] 22.1 [14.0, 34.0]	2.9 [1.7, 4.8] 3.3 [2.0, 5.2]	0.97 [0.58, 1.6] 1.1 [0.66, 1.7]
P-value ***		0.655	<0.0001	<0.0001	0.004
Age group, years  20–30  30–40  40–50  50–60  >60	416 (14.0) 694 (23.4) 802 (27.0) 787 (26.5) 267 (9.0)	6.8 [6.8, 6.8] 6.8 [6.8, 6.8] 6.8 [6.8, 6.8] 6.8 [6.8, 6.8] 6.8 [6.8, 6.8]	26.9 [17.9, 38.9] 22.6 [16.0, 34.0] 20.2 [12.5, 31.9] 19.9 [11.8, 31.6] 16.8 [10.5, 28.8]	4.3 [2.9, 6.3] 3.4 [2.3, 5.3] 2.8 [1.7, 4.5] 3.0 [1.7, 5.0] 2.8 [1.7, 4.2]	1.5 [0.96, 2.1] 1.1 [0.73, 1.7] 0.91 [0.56, 1.5] 0.95 [0.58, 1.6] 0.89 [0.59, 1.6]
P-value **		0.529	<0.0001 a	<0.0001 b	<0.0001 c
IgG reactivity at T0, AU/ml  <50  ≥50	2905 (97.9) 63 (2.1)	6.8 [6.8, 6.8] 134.4 [90.4, 322.8]	21.3 [13.3, 32.6] 32.5 [1.7, 4.2]	3.2 [1.9, 5.0] 7.7 [3.4, 12.4]	1.0 [0.64, 1.6] 3.1 [1.4, 5.4]
P-value ***		<0.0001	<0.0001	<0.0001	<0.0001

Data are presented as median and interquartile range.

*P-value <0.0001 for all comparisons between time points (Wilcoxon test).

**Kruskal-Wallis test, followed by Mann-Whitney tests. ^aP < 0.0001 for all comparisons except 40–50 vs 50–60 (P = 0.288), 40–50 vs >60 (P = 0.002) and 50–60 vs >60 (P = 0.027) (Mann-Whitney tests). ^bP< 0.0001 for all comparisons except 40–50 vs 50–60 (P = 0.238), 40–50 vs >60 (P = 0.745) and 50–60 vs >60 (P = 0.262) (Mann-Whitney tests). ^cP < 0.0001 for all comparisons except 40–50 vs 50–60 (P = 0.199), 40–50 vs >60 (P = 0.804) and 50–60 vs >60 (P = 0.535) (Mann-Whitney tests).

***Mann-Whitney test.

AU = arbitrary units.