CD19 and COVID-19: In the COVID-19 group at baseline, the lymphocyte counts and percentages (Fig. 3a, b), CD3+ cell counts (Fig. 4a), CD3+ CD4+ cell counts and percentages (Fig. 4c, d), CD3+ CD8+ cell counts (Fig. 4e), B(CD19+) cell counts and percentages (Fig. 5a, b), and NK (CD56+) cell counts and percentages (Fig. 6a, b) were all lower than the corresponding values in the control group.