7. Pioneers of COVID-19 vaccine program
Until February 9, 2021, 63 vaccine candidates to fight against SARS-CoV2
infection have entered clinical trials, while 179 candidates are going
through preclinical developments [52] (Fig. 1). Among the vaccine
candidates in clinical evaluation four inactivated, two protein subunit,
four adenovirus- and two mRNA-based vaccines constitutes the leading
candidates in the COVID-19 vaccine design scheme. Hereunto, only
BNT162b2, mRNA-1273 (mRNA-based) along with BBIBP-CorV and CoronaVac
(inactivated) vaccines have been emergency or conditionally approved in
some countries and the other candidates were allowed for early or
limited use [53] (Table 2).