A list of under-development vaccine candidates for COVID-19, according to the WHO as of 15 May 2020. Ref. – Draft Landscape of COVID 19 candidate vaccines, https://www.who.int/who-documents-detail/draft-landscape-of-covid-19-candidate-vaccines, accessed on May 15, 2020^a.

Vaccine platform/type of candidate	Immunogen/target	Current stage/phase of trial	Advantages	Disadvantages	Reference
RNA-based (mRNA-1273)	LNP-encapsulated mRNA VACCINE encoding the S protein	Phase 1 (NCT04283461), phase 1 (2020-001038-36), phase 1/phase 2 (NCT04368728)	Less infectious or mutagenic, short life span, chance of integration into the host genome is minimum, a low dose is required	Vaccines need optimal delivery agents, safety issues with unintended immune responses	166 and 167
Viral vector	Attenuated adenovirus capable of producing the spike (S) protein of SARS-CoV-2, ChAdOx1 (chimpanzee adenovirus vaccine vector)	Phase 2 (ChiCTR2000031781), phase 1 (ChiCTR2000030906), phase 1/phase 2 (NCT04324606)	High immunogenicity, long-term expression of infectious genes	Risk of pathogenesis and tumorigenesis	168
Subunit	Short antigenic peptide sequence	Pre-clinical AJ Vaccines, Epivax, Novavax, GSK/Sanofi	Induce both cellular and humoral immunity, chance of inducing diseases or side-effects is minimum	Multiple boosters required, an adjuvant is needed for delivery	169
Virus-like particles (VLPs)	Plant derived VLPs that mimic the shape and dimensions of the virus	Pre-clinical Medicago, Adaptvac	Can develop immunity against a multimeric protein at a given time	Assembly of VLPs in an expression vector is intricate	170 and 171
Inactivated	Inactivated SARS-CoV-2 + alum, inactivated SARS-CoV-2	Phase 1 (NCT04352608), Phase 1 (ChiCTR2000031809, ChiCTR2000032459)	Much safer as compared to a live attenuated vaccine, has been tested in the case of SARS-CoV-1	First dose does not always induce a robust immune response, antigenic integrity needs to be maintained	172 and 173
Live-attenuated virus	Whole virion	Phase 3 (NCT04328441), (NCT0432726) [BRACE] Pre-clinical Codagenix/Serum Institute of India	Memory cells are generated, producing the same effect as that of a live infectious pathogen	Might replicate in an uncontrolled manner, safety concerns	174 and 175
DNA-based (INO-4800)	DNA plasmid encoding the S protein	Phase 1 (NCT04336410)	Multiple variants of antigen can be inserted into a single plasmid	Chance of incorporation into the host genome, activation of oncogenes	176 and 177

^aBRACE: BCG vaccination to protect healthcare workers against COVID-19.