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. 2023 Apr 20;11(2):64. doi: 10.3390/diseases11020064

Figure 2.

Figure 2

A schematic diagram of current active development of SARS-CoV-2 vaccines as of September 2022. There are several types of vaccines which include (A) Inactivated viral vaccines, (B) Protein subunits vaccines, (C) Adenoviral vector vaccines and (D) mRNA vaccines. Aside from the whole inactivated virus in inactivated viral vaccines, other vaccines targeted the binding domain of SARS-CoV-2 Spike (S) protein. Moreover, the vector and mRNA vaccines targeted muscle cells at the injection site. The muscle cells produced some portion of the SARS-CoV-2 S protein, which is then presented by MHC Class I to antigen-presenting cells (APCs) and cytotoxic T cells. In contrast, inactivated viral vaccines and protein subunits vaccines are directly taken up by APCs. The APCs then presented the S protein antigen to T helper cells as well as B cells, which in turn activated sequential activities of humoral and cellular immune response against the SARS-CoV-2 S protein. These immunological activities also indirectly generate memory T cells and B cells for protection against future exposure against the virus. This image was created with Biorender.com.