PROS1 and COVID-19: Even COVID-19 vaccines are being developed using fusion proteins, such as NVX-CoV2373 (Novavax) (Dunkle et al., 2022), which uses recombinant spike protein trimmers; and S-Trimer (Clover Biopharmaceuticals), genetical fusion of SARS-CoV-2 S-protein to human C-propeptide of alpha1(I) collagen (Liang et al., 2020), promoting a self-trimerization and enabling purification via affinity chromatography.