PROS1 and COVID-19: For example, one can determine which SARS-CoV-2 protein or S protein peptide can induce significant antibody response, whether the antibody response against the inactivated virus vaccine differs from that of the live virus infection, the effectiveness of vaccination by comparing the antibody responses of vaccinated people and COVID-19 patients, and whether it is possible to identify peptide and/or protein combinations that may serve as surrogate biomarkers for convenient evaluation of the efficacy of vaccination and for differentiating COVID-19 patients from vaccinated individuals.