CD4 and COVID-19: Furthermore, in COVID-19 convalescents and vaccine recipients of the Moderna (mRNA-1273) or Pfizer/BioNtech (BNT162b2) COVID-19 vaccines, the original CD4+ and CD8+ T cell responses were comparable against the B.1.1.7, B.1.351, P.1, and CAL.20C lineages; however, amino acid epitope conservation was reduced in 7% of CD4+ T cell epitopes and 3% of CD8+ T cell epitopes (36, 39) (Table 1).