Correlations between immune responses per study arm.

Correlations were analysed at 28 days after the second vaccine dose between SARS-CoV-2 anti-RBD IgG binding antibodies and SARS-CoV-2 Wuhan neutralizing antibodies (A), and between SARS-CoV-2 Wuhan and Delta variant neutralizing antibodies (B). Pearson correlation coefficients (95% CI) are given per study arm. Ellipses represent the 95% CI for the two study arms (purple = 20μg, black = 30μg), assuming multivariate normal distributions. NT50 = 50% neutralizing antibody titre, RBD = SARS-CoV-2 receptor binding domain, BAU = binding antibody units.</p