To ascertain that S-protein–specific immune response was induced after SARS-CoV-2 vaccination, we utilized frozen PB samples collected from 17 heathy donors prior to the COVID-19 pandemic or before the first COVID-19 case was detected in the United States as control samples and assessed the cytokine production after coculturing the PBMCs with S-protein peptide pools. This evidence concerns the gene PROS1 and COVID-19.