Antibody assays
Recombinant SARS-CoV-2 spike antigens S1, S2, RBD, and spike antigens from hCOVs- HKU1, OC43, NL63, 229E were purchased from SinoBiological and nucleocapsid protein (NP) was kindly provided by André Matagne, University of Liège. All antigens were covalently coupled to fluorescent magnetic beads (Luminex Corporation) and were used to measure antigen-specific antibodies using the Fc array assay as described previously 15. Data was acquired on BioPlex-200 equipment (Bio-Rad) and the results were expressed as median fluorescence intensity (MFI). See the list of reagents in Supplementary Table I.