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The SARS-CoV-2 mRNA Vaccines

Author: William Tsay

Editors: Angela Pan and Hwi-On Lee

Artist: Acey Li

Every day, millions of coronavirus cases are reported. Many are sick of staying home and following CDC guidelines. The first coronavirus (SARS-CoV-2) case was reported in Wuhan, China on December 31, 2019, causing a worldwide pandemic. On December 11, 2020, the Pfizer-BioNTech vaccine was approved and available after numerous clinical trials. This vaccine was a breakthrough in modern medicine, as it was the first mRNA product to achieve full FDA approval in the U.S. Although the Pfizer vaccine uses mRNA to combat the virus, another vaccine, the Johnson & Johnson, uses the traditional vector method. Additionally, approving a vaccine for public use is long and complex; it requires the vaccine to pass a series of trials. What are the qualifications for a vaccine to be approved? How do the mRNA and the viral vector vaccine compare?

Making a vaccine is a slow and arduous process. The development of vaccines can take years or even decades. After the vaccine is produced, it goes through a series of preclinical tests. First, scientists test the new vaccine on the cells of animals, such as mice or monkeys, to see if it triggers an immune response. Then, the phase 1 safety trials begin—a small number of people are used to test the safety and dosage of the vaccine. The vaccine moves onto phase 2 or the expanded trials if the tests are successful. In phase 2, scientists give the vaccine to hundreds of people in different age groups. Children and the elderly are tested to see if there are different reactions to the vaccine. Finally, the phase 3 efficacy trials determine the possibility of rare side effects by giving the vaccine to thousands of people, comparing them to volunteers who received a placebo. When phase 3 is completed, regulators must review the trials and decide whether to give it full approval. At any phase of development, investigators can pause the trial. The trials may then be abandoned or resumed after investigation. There are currently 114 vaccines being tested in clinical trials on humans, and 47 have reached the final stages of testing.

The Pfizer-BioNTech mRNA vaccine contains engineered mRNA from the virus that causes COVID-19. After vaccination, the mRNA gives the cells instructions for how to make a harmless S protein found on the surface of the SARS-CoV-2 virus. The proteins created by the cells trigger the production of antibodies. If the virus later infects a host, the antibodies will be prepared to neutralize the danger. The mRNA that first enters the body never enters the cell's nucleus.

On the other hand, the vector vaccine uses a “viral vector” to enter the cells. When the viral vector enters the body, it gives the cells the instructions to make proteins, usually the S protein. Next, cells in the body will display the newly synthesized S protein on their surface, prompting the body to bump off the immune response by creating antibodies and white blood cells. Similar to the mRNA vaccine, the vaccine's contents never enter the cell's nucleus, where the DNA is being held.

The Pfizer-BioNTech mRNA and the Johnson & Johnson vector vaccines are similar in many ways. Nevertheless, these vaccines are a breakthrough in modern medicine, and hopefully, fewer cases will be reported with time.



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“The Different Types of Covid-19 Vaccines.” World Health Organization, World Health



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Medical Education and Research, 15 Jan. 2022,


Zimmer, Carl, et al. “Coronavirus Vaccine Tracker.” The New York Times, The New York

Times, 10 June 2020,


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