Published: 4 February 2021

COVID-19

mRNA Vaccines

mRNA vaccines are a new technology being used for preventing COVID-19 infection. One of the vaccines being developed is the Comirnaty COVID-19 mRNA vaccine (also known as the ‘Pfizer-BioNTech mRNA vaccine’).

What is mRNA?

Ribonucleic acid (RNA) is the genetic material in viruses such as SARS-CoV-2 (the COVID-19 virus). Once inside a human cell, SARS-CoV-2 RNA acts as messenger ribonucleic acid (mRNA), which is a type of molecule used by the virus as instructions for making the proteins it needs to function. Human cells generate mRNA for the same purpose.

How do mRNA vaccines work?

Vaccines prepare the body to defend itself against a specific disease. mRNA vaccines contain pieces of mRNA that tell the cells in the body how to make a viral protein that will be recognised by the immune system as foreign.

In this case, the mRNA contains instructions for the spike (S) protein on the surface of the SARS-CoV-2 virus. The S protein helps the virus enter human cells.

After the S protein copies are made in the body, the mRNA is broken down. The immune system recognises the S protein copies as foreign and makes immune cells and antibodies which can recognise and attack the SARS-CoV-2 virus via the S protein.

If the body is later exposed to the SARS-CoV-2 virus, the immune system is prepared to defend the body against illness. As a result some people may not get infected at all. Others will experience a much milder illness than they would have done without the vaccine.

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