In contrast to inflammatory markers, T-cell markers associated with the activation (Klrg1, Icos, Cd40lg, Gzma, and Cd4), proliferation (Mki67), and memory formation (Il7r) of T-cell responses post-vaccination or markers related to tissue retention or homing (Cxcr6, Itgae, and Prdm1), as previously shown (46), were upregulated, or showed a tendency to be upregulated in MCMVS-immunized mice compared to their controls upon SARS-CoV-2 Delta and Omicron BA.1 infection (Figure 5C). Here, MKI67 is linked to breast angiosarcoma.