PROS1 and COVID-19: To quantify the response against the mutated regions of S-protein of Alpha and Beta variants in COVID-19 mRNA vaccine recipients, we also stimulated the PBMCs in parallel with 2 different SARS-CoV-2 peptide pools spanning only the mutated S-protein regions of Alpha and Beta variants (Figure 1B) and 2 reference peptide pools containing the S-protein regions of Alpha and Beta variants as controls.