Enhanced vaccine-induced Spike-specific T-cell response in anti-CD19 CAR T cell–treated patients. Healthy individuals (n = 26) and (A) anti-CD19 CAR T cell–treated patients (n = 8) were vaccinated on days 0 and 21 with BNT162b2 mRNA vaccine. Blood samples were taken on days 0, 11, 21, 31, 42, and 90. (B) Levels of neutralizing antibodies. IFN-γ (C) and IL-2 (D) secreted into the plasma after whole blood stimulation with Spike-peptide pool and dimethyl sulfoxide control were quantified. (E) Representative flow cytometry plots for quantifying AIM+CD4 T cells. The numbers represent the percentage of total nonnaïve CD4 T cells that are AIM+ on days 0 and 42. Below, summary data of AIM+CD4 T-cell frequency before and after vaccination. The values represent the background-subtracted frequency of AIM+ nonnaïve CD4 T cells. (F) Representative flow cytometry plots for quantifying AIM+CD8 T cells. The numbers represent the percentage of total nonnaïve CD8 T cells that are AIM+ on days 0 and 42. Below, summary data of AIM+CD8 T-cell frequency before and after vaccination. The values represent the background-subtracted frequency of AIM+ nonnaïve CD8 T cells.