CD4 and COVID-19: A study in China analyzing lymphocyte subsets in 507 patients with COVID-19 also found that among 341 patients with COVID-19, the counts of T-lymphocytes, CD4+ T-lymphocytes, and CD8+ T-lymphocytes were significantly lower in the deceased group than in the recovered group, and that cellular immunity was more impaired in patients with severe and critical disease than in patients with mild disease [19].