• Absolute count of lymphocytes was decreased and specifically levels of CD4+ T and CD8+ T were lower in severe cases.• Higher levels of IL-2R, IL-6, IL-10, and TNF-α were observed in severe cases.• Higher levels of ALT, LDH, CRP, ferritin, and D-dimer was detected in severe cases.• Further, levels of IFN-γ levels specifically measured in CD4+ T cells were lower in severe cases.