SARS-CoV-2 vaccines and their challenges against the variants

The coronavirus disease 2019 (COVID-19) pandemic has lead to the several researches for the development of the new severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) vaccines. During this process, spike (S) protein (particularly in its prefusion [native] conformation) was identified as the immunodominant antigen of the SARS-CoV 2 virus1; it was found that the binding and neutralizing antibodies primarily target the receptor-binding domain (RBD) of the S1 subunit.2 After identifying the vaccine target, several SARS-CoV-2 vaccines were developed with an objective to achieve the response which include production of neutralizing antibodies, generation of a T-cell response, and avoidance of immune-enhanced disease. The SARS-CoV-2 vaccines that have been developed to combat COVID-19 are shown in the table 1.3