CD4 and viral infectious disease: (19) that observed the prevalence of central memory (CM) and effector memory (EM) subsets in Spike-specific CD4+ T cells and of CM, EM and terminally differentiated (EMRA) subsets in CD8+ T. Specific cellular immunity, mediated by T and B lymphocytes, can steadily respond and restrict viral infection, even in subjects with very low concentration of neutralizing antibodies (32, 33), thus preventing or reducing symptoms of COVID-19, and possibly reducing spreading of virus to others (34, 35).