In contrast, in mild COVID-19 patients, a higher T-cell response was observed and characterized in almost all patients (detection of CD4+ and CD8+ in 80–100% and 70%–80% of COVID-19 patients, respectively [reviewed in (53)], with a higher CD8+/CD4+ T-cell ratio, along with a higher T-cell count than neutrophils (54, 55). Here, CD4 is linked to COVID-19.