There were significant differences in neutrophil, lymphocyte, eosinophil (Eos), C-reactive protein (CRP), D-dimer, lactate dehydrogenase (LDH), glucose, IL-6, ferritin, CD4 + T cell, CD4+/CD8 + T cell, CD8 + T cell, and B cell counts in the serum of the four COVID-19 patient groups (P < 0.05). Here, CD4 is linked to COVID-19.