mRNA Vaccine: What it is and How it works?

When two pharmaceutical companies Moderna and Pfizer/BioNTech announced developments of mRNA (messenger RNA) vaccine against COVID-19, there is widespread optimism around the globe as it may limit COVID pandemics.

Scientists are evaluating nucleotide-based vaccines (DNA vaccine and RNA vaccine) for various diseases. So far, RNA vaccines are found to be safer and efficacious. (

Vaccines mimic an infectious agent and while doing so, they train the immune system to recognize the pathogen by producing antibodies and memory B/T cells. Traditionally, vaccines contain either a weakened strain of the pathogen (live-attenuated vaccine) or killed pathogens (mostly purified signature proteins of that pathogen) but in the case of mRNA vaccine, instead of an injection of protein, bodies get instructions to manufacture proteins.  

RNA Vaccine Technology (Image source: Harvard University)

Unlike traditional vaccines, mRNA vaccine is manufactured by chemical rather than biological synthesis. Thus, it is quicker and easier to produce mRNA vaccine as the laborious process of harvesting and purification proteins (by growing the virus in the eggs or animal cell lines) is not needed. The most notable limitation of mRNA vaccines is their inherent instability as they may break apart in above-freezing temperatures.

A comparison of traditional with the new mRNA vaccines. CC BY-SA

The most important challenge for the development of an mRNA vaccine remains its inherent instability because it is more likely to break apart above freezing temperatures. This is why the Pfizer-BioNTech mRNA vaccine needs to be optimally stored at minus 94 degrees Fahrenheit, but Moderna claims that its vaccine can be maintained at most home or medical freezer temperatures for up to six months.

How mRNA vaccine work?

If a person receives mRNA which encodes the viral protein, this person’s cells translate them to make viral proteins inside the body.  It is expected that within 24-48 hours of mRNA injection, protein level peaks inside the muscle cells and may last for a few days.

This protein antigen is presented by the antigen-presenting cells and triggers the activation of specific cells of the immune system. 

RNA Vaccine Technology (Image source: Harvard University)

Thus producing powerful antibodies (and memory B/T cells) that can neutralize the pathogen if the individual is ever infected by this pathogen.  

References and further readings

  • Hubaud A. (2015 May 5) RNA vaccines: a novel technology to prevent and treat disease. Harvard University.
  • Jackson, N.A.C., Kester, K.E., Casimiro, D. et al. The promise of mRNA vaccines: a biotech and industrial perspective. npj Vaccines 5, 11 (2020).

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. As an asst. professor, I am teaching microbiology and immunology to medical and nursing students at PAHS, Nepal. I have been working as a microbiologist at Patan hospital for more than 10 years.

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