COVID-19(28) SARS-CoV-2(28) Tocilizumab(16) Treatment(16) IL-6(16) Patient(16) COVID-19 patients(16) Cytokine storm(14) immune(13) severe COVID-19(13) occur(12) clinical(12) therapy(12) lead(11) cytokine(11) appear(10) Cytokine release syndrome(9) expression(9) immunosenescence(9) Immunotherapy(8) characterized(8) vaccination(8) disease(8) severity(8) dose(8) individual(8) humoral immune response(8) trajectory(7) syndrome(7) Critical(7)