CD8A and infection: Also, evidence of SARS-CoV-2 specific T cell memory in individuals exposed but not infected, so-called abortive infection, suggests that T cells have a defining role in rapid viral clearance and protection.105 110 These correlative studies have been confirmed by mechanistic studies in animal models, including non-human primate models that supported the role of CD8+ T cells, particularly in the case of waning antibody protection,121 and in phase 1 trials of adoptive T cell treatment with SARS-CoV-2 specific CD45RA memory T cells from convalescent donors to treat severe covid-19.122 123