Published: 4 February 2021
Revised:  15 April 2021


mRNA Vaccines

mRNA vaccines are a new technology being used for preventing COVID-19 infection. One of the vaccines s 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.

Copies of the S protein are made in the body. 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.

The mRNA is broken down shortly after vaccination. Animal studies showed that the mRNA in the Comirnaty vaccine is broken down within a couple of weeks.

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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