Fig. 4

Higher frequencies of SARS-CoV-2-reactive high avidity CD4 + and CD8 + T cells in children compared to adults. Comparison of SARSCoV-2 S-reactive T cells in children and C + V + subjects is demonstrated. Blood samples of 32 children and 27 C + V + were stimulated with SARS-CoV-2 peptides and analyzed by flow cytometry. (A) Frequencies of WT-, delta- and omicron-reactive CD4 + T cells among children and C + V+. (B) Frequencies of WT-, delta- and omicron-reactive CD8 + T cells. (C) Frequencies of WT-, delta- and omicron-reactive CD4 + CD3_low + T cells. (D) Frequencies of WT-, delta- and omicron-reactive CD8 + CD3_low + T cells. SARS-CoV-2 S-reactive CD4 + and CD8 + T cells are defined as CD4 + CD154 + CD137 + and CD8 + CD137 + cells respectively. Antigen-reactive responses were considered positive after the non-reactive background was subtracted, and more than 0.01% were detectable. Scatterplots show line at median. Unpaired data were compared with Mann-Whitney-test. P < 0.05 was considered significant, only significant p values are documented in the figures