Extended Data Fig. 1. Immunoassay distributions.

IgG antibody responses against SARS-CoV-2 spike (S, panels a-c), receptor binding domain (RBD, panels d-f) and nucleocapsid (N, panels g-i)) were measured for COV001 and COV002 participants in two laboratories: MSD and PPD. For 97 individuals, measures were available from both laboratories. The density distributions of measures from each laboratory for each antigen (panels a, d and g) and the correlation between intra-individual measures (panels b rho 0.98, e rho 0.98, and h rho 0.90) were inspected. If the density distributions overlapped and the intra-individual correlation (r²) was greater than 0.7, the original distributions were taken forward for analysis (as for S, panel c). However if r² was less than 0.7, the quintile normalised intra-laboratory measures were taken forwards for analysis (panels f and i).