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Figure 4.. Schematic mechanism of manufacturing of viral vector vaccines (A, adenovirus as example) and mRNA vaccines (B). The RNA of SARS-CoV-2 was sequenced, which identified the coding of surface proteins. Using endonuclease methods, an engineered mutated adenovirus vector that carries the SARS-CoV-2 surface protein gene was made. Different from the preparation of adenovirus, the mRNA sequences that encode the spike protein were directly generated. To enhance the stabilities of mRNA and to escape from human immunities, lipid nanoparticles were used to envelope the mRNA. After injection of both viral vector and mRNA vaccines, cells will read the mRNA sequence express the epitope of the surface protein (red within cell) in the cytoplasm or in the nucleus. This will trigger the host’s humoral and cellular immune responses that could potentially contribute to specific immunity to SARS-CoV-2.