Comparative studies have shown the potential to investigate the immunological status across various groups of COVID-19 patients, including those with differing disease severities and even asymptomatic or healthy individuals.28 In a study conducted by Wiech et al., they examined a group of patients who experienced a severe course of coronavirus infection.29 Their findings revealed a significant increase in the number of final effector cells CD8+ CD57+ six months after infection, accompanied by a substantial reduction in the population of naïve T-cells. Here, CD8A is linked to COVID-19.