Use of vaccine composition based on receptor binding domain of SARS-CoV-2 virus in development of protective immunity

The invention relates to the fields of biotechnology and medicine. The present invention describes the use of a vaccine composition based on the receptor binding domain of the SARS-CoV-2 virus in the treatment of patients recovered from COVID-19 and in those vaccinated with a vaccine platform other than a subunit vaccine that fails to develop an effective protective immunity, such as in the treatment of patients recovered from COVID-19, and in those vaccinated with a vaccine platform other than a subunit vaccine. Or when the protective immunization has declined over time and it is not suggested that a boost dose is administered with the same vaccine used in the primary immunization. In particular, the uses are described for vaccine compositions comprising a covalent conjugate between a receptor binding domain (RBD) and a carrier protein (e.g., tetanus toxoid, diphtheria toxoid, and CRM197), a vaccine composition having an RBD as an antigen and having or being free of a vesicle derived from the outer membrane