CD69 and myocarditis: As we observed significant differences in myocarditis-associated NK cell-specific cytokine profile in patients with different vitamin D status, we subsequently measured the early activation antigen CD69 expression on NK cells from patients with BNT162b2 vaccine-related myocarditis to confirm its correlation with clinical features and vitamin D status, in contrast to the non-specific activated HLA-DR+ monocyte subset (Figure 2).