Serological responses were detected against purified near-full-length trimeric SARS-CoV-2 viral spike glycoprotein by ELISA. A) Absorbance values of individual sera at a single dilution (1:40) from pre-2019 healthy adult donors (green) or sera from children with PIMS-TS (red), or plasma from adult ITU patients (orange) detected using combined HRP-labelled anti-IgG, IgA and IgM. One symbol represents results for a single serum and the bar shows the median values for each group. B) Absorbance values for individual sera from pre-2019 negative control donors (green), children with PIMS-TS (red), or plasma from adult ITU patients (orange) serially diluted five-fold from 1:50, primary antibodies were detected using HRP-labelled anti-IgG, IgA or IgM individually, or C) HRP-labelled IgG1 or IgG3.