NCAM1 and COVID-19: CD57 expression defines a functionally discrete sub-population of terminally differentiated and functionally senescent NK cells [33]. We detected a higher frequency (p < 0.001, Fig. 6D, E) and absolute number (p = 0.004, data not shown) of CD57+ve CD56 dim NK cells in severe COVID‐19 convalescent patients compared to healthy controls.