Fig. 1.

T-cell mediated immune response in NH residents 6 months (pre-booster, T6) and 12 months (postbooster, T12) after first immunization. (A) Frequencies of CD4 and CD8 T cells producing IFN-γ, TNF-α, and IL-2 in response to in vitro stimulation with spike. (B) Percentages of persons with nonresponding CD4⁺ and CD8⁺ T cells or producing 1 to 3 cytokines pre- and postbooster. Differences between median frequencies of cytokine positive T cells at T6 and T12 were calculated by the Wilcoxon test.