CD4 and viral infectious disease: Previous studies on SARS‐CoV‐2 have shown that Th2‐skewed CD4+ T cells are related to the induction of vaccine‐associated enhanced respiratory disease, while Th1‐biased immune responses enhance protection against viral infection.[33, 34] RBD‐RPT provoked more Th1‐biased IFN‐γ+ CD4+ T cells than other controls, whereas the percentages of Th2‐skewed IL‐4+ CD4+ T cells did not differ across the different groups (Figure 6b,c).