What are the different COVID-19 vaccines and how do they work?

Currently in the UK there are three vaccines available; Pfizer-BioNTech, Oxford-AstraZeneca and Moderna. The first two are being rolled out in the UK and the latter is expected to be available in the spring. These vaccines utilise alternative methods in order to provide immunity against the coronavirus. 

Pfizer-BioNTech and Moderna are both mRNA based vaccines which trigger an immune response in our body. mRNA or messenger RNA is a molecule found in all of our cells responsible for carrying the instructions for making the proteins that our genes provide instructions for. mRNA vaccines provide the genetic instructions for our cells to produce viral proteins, so our immune system can recognise what the pathogen looks like and begin to produce some antibodies for it. This means that when we are infected with the real pathogen our immune system can immediately recognise it and combat it. In the two mRNA COVID-19 vaccines the instructions carried are for part of the spike proteins found on the virus. These instructions are made in a lab and then packaged up in lipid nanoparticles, which make their way to our cells where the spike protein is manufactured. These proteins are recognised by our cells and trigger an immune response so that when we get infected by coronavirus our body immediately fights it.

The Oxford-AstraZeneca vaccine is a virus-based vaccine that acts as a Trojan horse to our body. It uses a chimpanzee adenovirus, which is a common cold in chimpanzees, as a vector. This type of virus is very well researched in vaccine technology and is commonly used as a vector, it is modified and weakened so that it is unable to grow in humans and infect them. As before, the virus contains the genetic code for the spike proteins on the coronavirus, so when the vaccine enters our body it produces the spike proteins and triggers an immune response so our bodies begin to produce antibodies for it. When we are infected with the real coronavirus our immune system can quickly recognise this and combat it.

These vaccines are also different in terms of storage, dosage, cost and efficacy. The Pfizer-BioNTech vaccine needs to be stored at -70 degrees Celsius, costs £15 per dose, requires 2 doses, 21 days apart and is considered to be 95% effective. The Oxford-AstraZeneca vaccine can be stored at standard refrigeration temperature, costs £3 per dose, requires 2 doses, 4-12 weeks apart and is considered to be 62%-90% effective. The Moderna vaccine needs to be stored at -20 degrees Celsius, costs £25 per dose, requires 2 doses, 28 days apart and is considered to be 95% effective. However it is important to recognise that no vaccine is 100% effective and there is always a risk that you may become ill after being infected.

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