CD4 and COVID-19: In an analysis of T-cell epitopes in humans recovered from COVID-19, the M and N antigens together accounted for 33% of the total CD4+ T-cell response (21 and 11% for M and N, respectively) and 34% of the total CD8+ T-cell response (12 and 22% for M and N, respectively), an amount exceeding the 27 and 26% CD4 and CD8 T-cell responses, respectively, of the S protein20.