CD4 and COVID-19: Univariable logistics regression analysis showed that variables with statistical significance including the counts of neutrophils, lymphocytes, CD4+ T cells, CD8+ T cells, CD 19+ B cells at week 2, as well as the levels of IL-2, IL-4, IL-6, and IL-10 at week 2 (Table S1); however, the multivariable analysis indicated that IL-6 was the only independent factor associated with the severity of COVID-19.