Fig. 2

cRBDs induced strong immune responses in BALB/c mice. a The timeline of vaccine immunization and sampling (created with BioRender.com). The serum used for cytokine detection was collected at 6 h and 24 h after the first injection. Final blood collection was performed at 14 and 21 days (Days 14 (n = 3), 21 (n = 3), 35 (n = 5), 42 (n = 5), 56 (n = 5), and 63 (n = 5) in (a)) after each immunization to collect serum for detection of vaccine-induced production of binding and neutralizing antibodies. Spleens were collected simultaneously 21 days after the third injection (day 63) for an ELISPOT assay. b Fold change in the levels of inflammation-related cytokines in the serum at 6 h and 24 h after immunization (n = 5). The color of the circle represents the P-value. The smaller the P value is, the redder the color. The size of the circle represents the fold change (FC). FC = cytokine level at 6 h after immunization /cytokine level at 24 h after immunization. The greater the FC is, the larger the circle. c–f BA.2 RBD-specific binding antibody levels at each time point after immunization in each group. Data are presented as mean ± SD