Procedures
Binding antibodies were measured by singleplex bead-based immunoassays on the Luminex platform to quantify serum IgG binding to full length spike and RBD of wild type; and reported in binding antibody units per millilitre (BAU/mL) as described (Neutralising antibody responses were evaluated in a convenience subset of samples, which screened positive for anti-S IgG and for which sufficient residual sample was available for pseudovirus neutralising antibody assay (PSVN) testing. Pseudovirus neutralisation assays were as described.