Functional characterization of severe acute respiratory syndrome coronavirus 2–specific T cells (CoV-2-STs) from convalescent, unexposed, vaccinated, and asymptomatic donors. A and B, Interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) secretion of the CoV-2-STs generated from convalescent (dots; n = 14), unexposed (squares; n = 16), vaccinated (triangles; n = 11), and asymptomatic (rhombuses; n = 4) individuals upon stimulation with their initial stimuli. Each dot represents a single T-cell product. Differences between data sets were analyzed using Kruskal-Wallis test. *P ≤ .04; **P ≤ .0043; ***P ≤ .0007; ****P < .0001. C, Percentage of killing of autologous, peptide-pulsed, or allogeneic unpulsed Phytohemagglutinin (PHA) blasts by CoV-2-STs. Differences between data sets were analyzed using Kruskal-Wallis test vs the respective unexposed donor condition or allogeneic unpulsed PHA blasts or irrelevant-peptide condition. ****P < .0001. D, IFN-γ and TNF-α secretion of the CoV-2-STs generated from convalescent (light colored boxes; n = 3-14) and vaccinated (dark colored; n = 4-11) individuals upon stimulation with spike antigen of SARS-CoV-2 or its B.1.1.7 and B.1.351 variants. E, Percentage of killing of autologous, unmutated spike-, B.1.1.7 or B.1.351 spike-pulsed PHA blasts by CoV-2-STs. Abbreviations: Conv, convalescent donor–derived T-cell product; CoV-2-ST, severe acute respiratory syndrome coronavirus 2–specificT cell; IFN-γ, interferon gamma; NCAP, Nucleocapsid; SFC, spot-forming units; TNF-α, tumor necrosis factor alpha; Unex, unexposed individual–derived T-cell product; Vac, vaccinated donor–derived T-cell product.