Fig. 4

IFN-γ secretion of CD8⁺ cells in naïve mice immunized by WT and variant RBD mRNA vaccines. Mice were immunized with various RBD mRNA and the Bivalent vaccines as described in Fig. 3. A, B IFN-γ secretion capacity of CD8⁺ cells against SARS-CoV-2 (CoV-2) spike RBD peptide measured by ELISpot assay. Representative spot images were shown in A and summary spot counts shown in B. SFC, Spot forming cells. Statistical comparisons across groups were determined by one-way ANOVA with Tukey’s multiple comparisons test. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. ns non-significant. See also Additional file 1: Fig. S4