Among previous naturally infected patients, the median level of S-protein IgG 30 days after the second dose of BNT162b2 vaccine was higher: 706.45 UA/mL(157.97–983.2), or greater >1000 UA/mL in 8/24 subjects (33%) in comparison to antibody levels in patients without prior COVID-19 history: 195.7 UA/mL (99.20–349.67). This evidence concerns the gene PROS1 and COVID-19.