Fig. 4. T cell and antibody responses of mRNA- and heterologous-vaccinated individuals after booster vaccination.

(A to D) Time course of spike antibody titers (A and B) and intensities of ex vivo IFN-γ T cell responses in terms of calculated spot counts were assessed by IFN-γ ELISpot assays targeting spike-specific peptide pools (C and D) after mRNA (A and C) and heterologous (B and D) vaccination before (V0), 1 month after the first (V1) and complete vaccination (CV), 6 months after complete vaccination (CVT2), and 1 month after boost vaccination (BV). For results of paired samples from the same donors at each time point, please refer to fig. S9 (paired samples n = 8 for heterologous vaccination and n = 2 for mRNA vaccination). (E and F) Intensities of ex vivo IFN-γ T cell responses against the SARS-CoV-2 BA.1 and BA.2 mutation pools at complete vaccination and boost vaccination for mRNA- and heterologous-vaccinated donors, respectively. Responders are represented by colored symbols, and nonresponders are represented by clear symbols. (G to L) T cell responses were characterized by ex vivo intracellular cytokine and surface marker staining. T cell responses were considered positive if the detected frequency of cytokine-positive CD4⁺ or CD8⁺ T cells was ≥3-fold higher than the frequency in the negative control and minimum of 0.1% of total CD4⁺ or CD8⁺ T cells. (G and H) Percentage of individuals with CD4⁺ (top), CD8⁺ (middle), and both CD4⁺ and CD8⁺ (bottom) ex vivo T cell responses to spike-specific peptide pools during the course of mRNA (G) and heterologous (H) vaccination. (I and J) Heatmaps showing the percentages of cytokine- and surface marker–expressing CD4⁺ and CD8⁺ T cells ex vivo after complete and boost vaccination after mRNA (I) and heterologous (J) vaccination. (K) Proportion of TNF⁺CD4⁺ spike-specific T cells expressing the T cell memory marker CD45RO after complete vaccination (n = 12 and n = 7) and boost vaccination (n = 8 and n = 8) for mRNA- and heterologous-vaccinated donors, respectively. (L) Proportion of IFN-γ⁺CD8⁺ spike-specific T cells expressing the T cell memory marker CD45RO after complete (n = 3 and n = 0) and boost vaccination (n = 4 and n = 1) for mRNA- and heterologous-vaccinated donors, respectively. (A and B) Antibody titers are shown in units per milliliter (1 U/ml corresponds to 21.80 binding antibody units/ml). (A to D) Data are presented as scatter dot plots with the median, and whiskers show the maximum. (E and F) Box plots show the median with the 25th and 75th percentiles, and whiskers represent the minimum and maximum. (K and L) Data are presented as scatter dot plots with the mean, and error bars indicate SD. (A, K, and L) Mann-Whitney U test was used. (B to F) Kruskal-Wallis test was used. (G and H) Fisher’s exact test was used. If P values are not shown, then results were not significant.