Fig. 5: CD8⁺ T effector cell response after breakthrough infection and the 4^th vaccine dose.

Calculated ex vivo frequencies of spike-specific CD8⁺ T cells before and after breakthrough infection and 4^th vaccination (a). Proportion of CD38⁺, Ki-67⁺ and T-BET^hi within non-naive spike-specific CD8⁺ T cells at peak expansion after breakthrough infection and 4^th vaccination with n = 11 for Omicron and n = 2 for Delta breakthrough infections, and n = 4 individuals receiving a 4^th vaccination (b). Statistical significance was calculated by two-way ANOVA with main model to compare the effects of antigen triggers (p_a) on epitope-specific T cell frequencies (a) and two-way ANOVA with full model and Tukey’s test for multiple comparison (b) to examine the effects of antigen triggers on activation marker expression. Source data are provided as a Source Data file.