Table 2.

Key features of COVID-19 candidate vaccine types in Phase 3 clinical trials, as of 27 September 2020.

Type of Candidate Vaccine	Key Features
Viral Vectored Vaccines	Consist of recombinant virus (viral vector), in which the genome of the unrelated, harmless virus is used to deliver the antigen into human cells [21]
Inactivated Vaccines	Vaccine that contain inactivated virus that is inactivated by chemical, radiation or physical methods, which is no longer infectious [22]
RNA (mRNA)	Encodes a stable perfused form of Spike protein (antigen) and delivers to human cell. Once delivered, the human cell produces a vaccine antigen from the genetic code [23]