CD4 and COVID-19: The major differences between the proportion of COVID-19 patients and healthy donors (p < 0.0001 for CD4+, Fig. 1a; p < 0.0001 for CD8+, Fig. 1b), or between close contacts and healthy donors (p < 0.0001 for CD4+, Fig. 1a; p = 0.0157 for CD8+, Fig. 1b) with memory T-cells capable of proliferating in response to SARS-CoV2 peptides emphasize that exposure to SARS-CoV-2 can facilitate the establishment of the T memory immunity not only in COVID-19 patients, but also in some close contacts even in the absence of a successful infection.