Outcomes
S-protein IgG against the SARS-CoV-2 Receptor-Binding Domain (RBD) of the S1 subunit was detected using the SARS-CoV-2 IgG II Quant assay (Abbott Diagnostics). Results were expressed as arbitrary units per mL (AU/mL; positive threshold: 50 AU/mL; upper limit: 40,000 AU/mL; a level ≥ 1,050 AU/mL was considered as a significant response21 and a level ≥ 4160 AU/mL as a level indicating a high neutralising effect according to the manufacturer). N-protein IgG were detected using the SARS-CoV-2 IgG assay (Abbott Diagnostics). Results were expressed as signal to cutoff ratio (S/CO; Abbott Alinity; positive threshold: 0.8 S/CO) 22 .