a, b, Serum anti-S IgG titres (a) (half-maximal effective concentration (EC50)) and live-virus neutralizing antibody titres (b) (half-maximal inhibitory concentration (IC50)), measured by enzyme-linked immunosorbent assay and focus reduction neutralization titre assays, respectively. c, Live-virus neutralizing antibody response against the wild-type (WA1) or B.1.351 variant measured in day-42 sera. d, e, Spike-specific CD4 (d) and CD8 (f) T cell IFNγ response in blood. Each dot represents a participant (n = 56 (a, b), 30 (c) and 38 (d, e)). Statistical differences were calculated using two-sided Wilcoxon matched-pairs signed-rank test. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. Boxes show median and 25th–75th percentiles, and whiskers show the range.