Table 1.

Immunological significances of all vaccine candidates against SARS-CoV-2

Vaccine platform	Type of antigen	Type of immune response	Neutralizing antibody response	T cell response		Immunogenicity and required dose (s)	References
				CD4 + Th cell	CD8 + T cell
Inactivated	Inactivated SARS-CoV-2	Antibody and/or cell mediate response	Strong response	Th1 cell or Th2 cell depending on adjuvant	Weak response	Weak; requires two or more doses	[52, 64]
Live attenuated	Weakened SARS-CoV-2	Antibody and/or cell mediate response	Strong response	Th1 cell	Strong response	Strong; requires a single dose	[52, 64]
Protein Subunit	SARS-CoV-2 spike protein	Antibody and/or cell mediate response	Strong response	Th1 cell or Th2 cell depending on adjuvant	Weak response	Weak; requires two or more doses	[52, 64]
Virus-like particles (VLPs)	Multiple proteins of SARS-CoV-2	Antibody mediate response	Strong response	Th1 cell or Th2 cell depending on adjuvant	Weak response	Weak; two or more doses	[52, 64]
Viral vector	Nucleic acid of SARS-CoV-2	Antibody and/or cell mediate response	Depends on pre- existing anti-vector immunity	Th1 cell	Strong/weak response depends on spike protein vaccines (replicating and non-replicating	Strong, weak or moderate; requires two or more doses	[52, 64]
DNA	Nucleic acid of SARS-CoV-2	Antibody and/or cell mediate response	Depends on pre- existing anti-vector immunity	Th1 cell	Moderate response	Weak; requires two or more doses	[52, 64]
RNA	Nucleic acid of SARS-CoV-2	Antibody and/or cell mediate response	Depends on pre- existing anti-vector Immunity	Th1 cell or Th2 cell depending on adjuvant	Strong/weak response depends on the choice of adjuvant and formulation	Strong, weak or moderate; requires two or more doses	[52, 64]