We found that the absolute counts of T-lymphocytes and their subpopulations in the peripheral blood of patients with COVID-19 are reduced, and the proportion of each subpopulation was disproportionate, the absolute counts of T-lymphocytes and their subpopulations in the peripheral blood of critically ill patients are lower than those of mildly ill patients, and the absolute CD8+ T-lymphocyte count in the peripheral blood of patients with COVID-19 is negatively correlated with the age of the patients. Here, CD8A is linked to COVID-19.