CD4 and COVID-19: Nevertheless, an association between low CD4+ T-cell counts and increased risk of hospitalization, ICU admission and mortality from COVID-19 has been observed [33,107,170,187,188,191,192], with a cut-off point for defining a low CD4+ T-cell count of <200 cells/mm3 having been established in some studies [33,167,189] and of <350 cells/mm3 in others [187,191,193].