Vaccines: The Endemic

Vaccines have been one of the most important scientific discoveries in history, preventing more than 2.5 million deaths each year, according to The World Health Organisation. The principle of vaccines is to recreate the natural immune response to a disease, without infecting the individual. It is due to worldwide and sustained vaccination efforts that smallpox has been eradicated, and the prevalence of diseases such as polio, measles, and tetanus dramatically reduced. Currently, it is a systematic vaccination programme which has reduced the risk of death and serious illness due to coronavirus, and it is the coronavirus vaccine that I will primarily be discussing in this blog.

However, to understand the how vaccines work, we must first understand the mechanism behind an immune response, and I’ll use the analogy of a night club security team to help me explain. Normally, when a harmful foreign molecule enters the body, it is met by the body’s bouncers, called an antigen presenting cell. This bouncer decides if the molecule is harmful, and if it is, restrains it, takes its ID (its antigens) and gives the ID to its manager: an immune cell, called a T-cell. The Manager calls their head of security, another immune cell called a B-cell, who takes the ID of the harmful molecule and creates a protein, called an antibody, which will continuously scan the body (the nightclub) for that specific foreign molecule, in case it manages to sneak back in to cause harm. If the foreign molecule enters the body again, the antibodies recruit different bouncers to fight against the foreign molecule before it can cause harm – this is an immune response.

Traditional vaccination puts a small amount of an inactive harmful foreign molecule into the body. This is the equivalent of a harmful foreign molecule being ‘blacklisted’, still using the nightclub analogy, it’s like another club sharing an ID of a person to warn you to keep an eye out for them. The molecule is inactive, but has the antigens which uniquely identify them and triggers an immune response to produce antibodies. Because of this, you can be protected against the disease without it ever entering the body.

But what has any of this got to do with genetics? Well, the coronavirus pandemic saw the first global use of an mRNA vaccine. mRNA is a length of genetic material which instructs the body to make specific proteins, and most of the cells in our body contain machinery which turns this mRNA into proteins. Although Pfizer, Moderna, Astra Zeneca and Johnson and Johnson vaccines are all mRNA vaccines, they do work in slightly different ways. However, the principle is the same for them all: a small amount of mRNA from a coronavirus molecule is injected into a cell, and the machinery already found in cells uses this mRNA to make a harmless protein called a spike protein. This spike protein is found on the surface of the coronavirus molecule and identifies it as coronavirus. The body detects that there is a foreign harmful molecule in the body and triggers an immune response. That way, if the body detects the spike protein again (this time attached to a covid-19 molecule), it will immediately trigger an immune response to kill the virus. 

Essentially, traditional vaccinations is the equivalent of injecting the spike protein into the body, whereas with mRNA vaccinations, you make the spike protein yourself within the body.

The only difference between these vaccines is how the mRNA molecule is delivered into the body. Pfizer and Moderna vaccines inject a small amount of mRNA from a covid-19 virus, wrapped in a fatty coat to stop it degrading. Once it enters the cell, the mRNA is unwrapped from the fatty coat and used to make the spike protein. Johnson and Johnson and AstraZeneca use something called a vector. This vector uses genetic material, called a plasmid, from a harmless, unrelated bacteria. The mRNA from coronavirus is inserted into the vector’s genetic material and this vector is injected into the body, then mRNA is used to make the spike protein. The important part is that whilst these vaccines use genetic material, they do not change the individual’s own DNA. This is because the DNA is stored in a different place in the cell from where the mRNA is used to make proteins.

Overall, it is the incredible discovery and use of mRNA vaccines to fight coronavirus which has helped save lives and reduce serious illness due to the virus. Like many, I believe it has, almost singlehandedly, brought us closer to the end of the pandemic and back to some normality. The scientists who developed the breakthrough and healthcare workers who deliver the vaccines deserve endless praise and respect for their efforts, as we will forever be in their debt.

References

https://www.savemyexams.co.uk/a-level/biology/cie/22/revision-notes/19-genetic-technology/19-1-principles-of-genetic-technology/19-1-5-genetic-engineering-vectors/

https://www.auckland.ac.nz/en/news/2021/02/24/how-the-pfizer-vaccine-for-covid-19-works.html

https://www.bbc.co.uk/bitesize/guides/ztp9q6f/revision/6

https://www.bupa.co.uk/newsroom/ourviews/covid-19-vaccine-facts

https://www.cdc.gov/coronavirus/2019-ncov/downloads/vaccines/COVID-19-mRNA-infographic_G_508.pdf

Disclaimer

The information in this blog is for information and entertainment purposes only. I am not a medical professional, so I have never and will never give medical advice in this blog. You should always speak to a healthcare professional about your unique health needs. My opinions are entirely my own and do not reflect the organisations or people I work for. I only discuss published literature in this blog which are referenced with links.

 

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