CD8A and COVID-19: The main findings in our study were as follows: (1) more than half of COVID-19 patients were positive for EBV VCA IgM antibody; (2) EBV VCA IgM antibody was associated with fever, higher CRP and higher AST; (3) the EBV/SARS-CoV-2 coinfection patients were more likely to be given corticosteroid therapy by doctors; (4) The CD8 count in EBV/SARS-CoV-2 coinfection patients was a litter less than that in SARS-CoV-2 infection alone patients.