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 .