The clinical effect of immunity against seasonal coronaviruses on COVID-19 was shown in the work of Yamaguchi et al. This group studied the titers of antibodies against S-proteins of SARS-CoV-2 and HCoV-OC43 in patients hospitalized with COVID-19, and analyzed the correlation between antibody titers and the severity of each case. This evidence concerns the gene PROS1 and COVID-19.