CD8A and COVID-19: All these results consistently point out that even though the CD8+ T-cell response in all symptomatic patients, regardless of the disease severity, starts with the mounting of (pre-existing) T cells specific to CoV-common epitopes during the first week after the symptom onset, only individuals with non-critical COVID-19 appear to be effectively activating and expanding T cells recognizing SC2-unique epitopes during the first two weeks of the disease.