Most effective vaccines for COVID-19 and their mechanism

COVID-19 is caused by the SARS-CoV-2 virus, which belongs to the same viral family that also caused SARS and MERS. Once the virus enters the body, it attaches to the cellular surface by utilizing its spike proteins on the viral surface. Then the virus deceives the cellular metabolic system and multiplies uncontrollably. To become immune to the COVID-19, antibodies should be taught how to identify and remove those “foreign” viruses for several times. Vaccines teach our antibodies by mimicking viral infection with inactivated viruses or components of the viruses. The followings are most prominent COVID-19 vaccines and their mechanism.

Among nine COVID-19 vaccines that currently have been approved, three are considered most promising: BNT162b2, mRNA-1273, AZD1222 from Pfizer, Moderna, and AstraZeneca respectively. BNT162b2 was approved by Food and Drug Administration (FDA) on December 11, 2020, and Medicines and Healthcare products Regulatory Agency (MHRA) on December 2, 2020. Since then, UK has begun their public vaccination. The efficacy of the vaccine is 96 percent. In addition, mRNA-1273 was also approved by FDA on December 18,
2020, and with 94 percent efficacy. Lastly, AZD1222 was approved by MHRA on December 30, 2020 with 70 percent efficacy.

In BNT162b2 and mRNA-1273, insoluble organic compounds (lipid nanoparticles) contain mRNA, a genetic material, to synthesize the viral spike proteins. On the other hand, AZD1222 contains the DNA of the spike proteins, but the DNA is enveloped in a different type of virus. mRNA vaccines are more fragile than DNA. In an aspect of storage, this means that mRNA vaccines require an extremely cold environment (-80°C) while DNA-based vaccines can be stored from 2°C to 8°C.

BNT162b2 and mRNA-1273 prevent people from SARSCoV- 2 virus infection by not allowing the viral spike to attach to the cellular surface. After the spike protein genes
reach the human cell, spike proteins are formed in our bodies. When the spikes are detected, they activate the human immune system; antibodies are produced to identify
and remove the “foreign” proteins in case SARS-CoV-2 virus enters the body. Because BNT162b2 and mRNA- 1273 only contain the spike proteins, there is no chance the host will be infected by COVID-19.

AZD1222 works the same way as the two vaccines above in the aspect that it also carries a genetic material for spike synthesis but differs in the method of delivery. DNA for the spike is contained in an inactivated adenoviral vector which is a delivery tool originated from a chimpanzee common cold (adenovirus). The vector is modified so that it does not replicate uncontrollably and so does not the spike DNA. Using a modified adenoviral vector guarantees high specificity for DNA to reach the cell. Vaccination had been given to 268.57 million people until March 2, 2021 in the world. Moreover, BNT162b2, mRNA-1273, and AZD1222 have been approved in 50, 36, and 7 countries, respectively.

저작권자 © 건국불레틴 무단전재 및 재배포 금지