These observations suggest that, in addition to chronic periodontal inflammation, hyperactivated and reduced levels of CD4+ and CD8+ T cells are implicated in immune injury and the onset of cytokine storm in the lungs and other vital organs of patients with COVID‐19, which are associated with severe COVID‐19 cases, COVID‐19‐induced pneumonia, and death. The gene discussed is CD4; the disease is susceptibility to pneumonia measurement.