CD8A and COVID-19: Pre-existing T cell responses in were observedfor 81% of unexposed individuals.257 Onthe other hand, Ferretti et al. reported SARS-CoV-2 epitopes thatare widely shared by CD8+ T cells of COVID-19 patientsbut show low cross-reactivity with other seasonal coronaviruses.258 All memory CD8+ T cells for a particularCOVID-19 patient were screened, for every HLA allele, against everyepitope in the SARS-CoV-2 virus and the four seasonal coronavirusesresponsible for the common cold.