a Schematic showing SARS-CoV-2 S trimer, S1 and RBD. b ELISA measurement of plasma reactivity to RBD, S1, and S trimer. Y-axis is OD 450 nm normalized to the mean absorbance of CR3022 in each plate. X-axis is log reciprocal plasma dilution (upper row). Normalized area under the curve (AUC) of 18 controls (gray) and 45 patients (35 patients infected with SARS-CoV-2, red; 4 patients infected with HCoV-OC43, blue; 5 patients infected with HCoV-HKU1, green; and 1 patient infected with HCoV-229E, magenta) for IgG binding to SARS-CoV-2 S1, S trimer, and RBD (lower row). Data were expressed as mean. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. c Correlation between AUC of anti-SARS-CoV-2 RBD and AUC of anti-SARS-CoV-2 S1 (left) or anti-SARS-CoV-2 S trimer (right). d Correlation between AUC of anti-SARS-CoV-2 RBD and AUC of anti-SARS-CoV RBD. e Demographic details and normalized AUC of all samples for IgG binding to β-CoV (SARS-CoV-2 S1, S trimer, RBD, SARS-CoV RBD, MERS-CoV S1, and HCoV-HKU1 S1) and α-CoV (HCoV-229E S1 and HCoV-NL63 S1) presented in bar chart.