CD4 and infection: To assess the impact of the mutations in the spikes of other Omicron variants on the pre-existing T cell responses after infection with the Omicron BA.5/BF.7, mutant peptides from Omicron variants such as BA.1, XBB.1.5, CH.1.1, EG.5.1, and JN.1 were respectively employed to stimulate splenocytes of the pVAX-BA.5 vaccinated mice to evaluate specific IFN-γ+ CD4+ and CD8+ T cell responses.