Specifically, correlations among low frequencies of naïve CD4+ and CD8+ T cells, age, and COVID-19 disease severity have been observed (Rydyznski Moderbacher et al., 2020; Zhang et al., 2020); however, whether these observations are a cause or consequence of severe COVID-19 that causes a drastic change in T cell phenotypes, including lymphopenia (Chen and John Wherry, 2020; Huang et al., 2020), is not well understood. This evidence concerns the gene CD4 and COVID-19.