To investigate whether different breakthrough infections and I-I-I vaccination could lead to different levels of SARS-CoV-2-specific T-cell responses, levels of IFN-γ+CD4+ and IFN-γ+CD8+ T cells were measured as virus-specific T cells by intracellular cytokine staining after ex vivo stimulation with the peptide pools of S/M/N/E and RBD. Here, CD4 is linked to infection.