PROS1 and COVID-19: As the Sinopharm BBIBP-CorV vaccine induced T cell response targeting N and membrane (M) proteins similar to cell-mediated immune response in patients who recovered from COVID-19 [25], not the case with Pfizer-BioNTech vaccine, isolated the measurement of S protein-binding antibody titers after the COVID-19 vaccines is not sufficient to conclude the immune efficacy of Sinopharm BBIBP-CorV and other inactivated vaccines [28].