Figure 4.

Schematic summary of the various types of vaccine candidates developed against SARS-CoV-2. The vaccine types are illustrated and categorized into several key technologies. (A) Protein subunit—vaccine candidates that use pieces of the virus protein to elicit an immune response without using live components. (B) Viral vector (non-replicating or replicating)—vaccines. The virus is modified to deliver genetic material of SARS-CoV-2 to induce an immune response. (C) DNA or RNA—vaccines. Genetic material is applied to encode antigenic parts of the virus that are expressed in the host to induce immunity. (D) Inactivated virus. These vaccines contain virus particles that have been killed or inactivated but still elicit an immune response. (E) Virus-like particles—mimic the virus structure but lack viral genetic material, typically focusing on the virus's outer protein coat. (F) Live attenuated virus—vaccines that use a weakened form of the virus that can still replicate without causing illness. (G) Viral vector plus antigen presenting cell (non-replicating or replicating)—combines viral vector technology with cells that effectively present antigens to the immune system. (H) Bacterial antigen-spore expression vector—employs bacterial spores to express the SARS-CoV-2 antigen, presenting a novel vaccination strategy. (Created with BioRender.com).