In this study, we report that two simple IgG ELISAs can distinguish COVID-19-naïve (both anti-N and anti-S negative), COVID-19-naïve vaccinees (anti-S positive only), or COVID-19-recovered cases with or without vaccination (both anti-N and anti-S positive) in places where only S-based vaccines, such as mRNA, adenovirus-vectored, and recombinant S protein vaccines are implemented. This evidence concerns the gene PROS1 and COVID-19.