Fig. 3: Analysis of RBD-specific memory B cells and spike-specific memory T cells in vaccinated individuals.

a–e, Flow cytometry analyses of spike-specific mBCs. a, Frequencies of SARS-CoV-2 RBD-binding mBCs among the pool of polyclonal mBCs before vaccination, after prime and after boost injections. b, c, Proportions of unswitched (b) and switched (c) RBD-binding mBCs in per cent of RBD-binding mBCs. d, Pattern of immunoglobulin isotypes expressed by switched mBCs. e, Proportions of resting (CD21⁺CD11c^–) and activated (CD21^–CD11c⁺, CD21^–CD11c^– and CD21⁺CD11c⁺) mBCs among the entire pool of RBD-binding mBCs. f–h, T cell responses. f, IFNγ release after whole-blood stimulation with RBD peptides. IFNγ was measured by ELISA in the supernatant. g, h, Flow cytometry analyses of the percentage of cells positive for intracellular IFNγ expression among CD4 (g) or CD8 (h) T cells after PBMC stimulation with commercial spike peptides. In all panels, box-and-whiskers plots (see Methods for details) of n = 29 and n = 31 participants in heterologous and homologous vaccination groups, respectively, are shown. The median value is shown in each group as a purple line. A high cellular mortality rate at the thawing step led to the exclusion of a few samples in each panel; each individual dot corresponds to one participant, and each measurement was performed once. In all panels, a linear regression model was used to compare values between groups, and this model was corrected for age. Exact P values are shown for the indicated comparisons when significant or nearly significant.

Source data.