TABLE 1.

Serum Levels of anti-SARS-CoV-2 Antibodies (Median and Interquartile Range) in Baseline SARS-CoV-2 Seronegative and Seropositive Healthcare Workers, Undergoing BNT162b2 mRNA COVID-19 Vaccination

	Baseline			21 days			50 days
Antibodies	Seronegative	Seropositive	P ∗	Seronegative	Seropositive	P ∗	Seronegative	Seropositive	P ∗
Anti-SARS-CoV-2 RBD Total Ig (AU/mL)	0.4 (0.4–0.4)	92.5 (15.9–141.5)	<0.001	57.2 (21.2–98.0)	20,585.5 (11,902.0–24,527.5)	<0.001	1629.0 (1136.3–2587.0)	19,984.0 (14,394.8–25,000.0)	<0.001
Anti-SARS-CoV-2 RBD IgG (AU/mL)	0.2 (0.1–0.2)	10.0 (8.0–14.4)	<0.001	41.7 (23.1–88.1)	340.4 (241.8–433.2)	<0.001	341.2 (263.7–641.2)	306.4 (262.7–358.2)	0.068
Anti-SARS-CoV-2 S1 IgA (ratio)	0.23 (0.16–0.31)	1.17 (0.78–1.70)	<0.001	3.15 (2.02–5.65)	8.97 (8.79–10.41)	<0.001	5.76 (3.67–7.28)	8.76 (8.01–9.75)	<0.001

Ig, immunoglobulin; RBD, receptor binding domain; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

^∗Seropositive vs. seronegative.