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The Covid Vaccines – What Does It Do? Part 1

June 7, 2021

Let’s start with the vaccine itself.

Vaccine ingredients

Vaccine ingredients vary depending on what the vaccine is for. They may contain some of the following ingredients:

  • a protein component of a virus
  • a piece of genetic code (DNA or mRNA)
  • a very small dose of a weakened virus
  • a substance to boost the immune response (an adjuvant)
  • -a small amount of preservative
  • -sterile salt water (saline) for injections.

The vaccines available now in Australia are the Pfizer and AstraZeneca. Eventually the Novavax vaccine will be introduced later in the year. They are all two dose vaccines.

Comparing Australia’s three COVID-19 vaccine options. Jamie Triccas, made with BioRender, CC BY-ND

The protein part of the vaccine is the coronavirus’ “spike protein”.

Each vaccine introduces a form of “Spike proteins” into the body to cause an immune response. These spike proteins cause the viral infection. The body makes antibodies to this which will stop the infection jumping from cell to cell in the body.  

AstraZeneca COVID-19 Vaccine – Uses a chimpanzee adenovirus to carry spike proteins from the coronavirus into your body to create an immune response.

Pfizer COVID-19 Vaccine – The ingredients are mRNA, lipids, potassium chloride, monobasic potassium phosphate, sodium chloride, dibasic sodium phosphate dihydrate, and sucrose.  The mRNA is delivered to your body’s cells by lipid nanoparticles, and instructs the cells to generate the spike protein found on the surface of the novel coronavirus that initiates infection, instructing cells to generate the spike protein spurs an immune response, including generation of antibodies specific to the Covid 19 spike protein.

mRNA vaccines do not contain any virus particles, meaning that they don’t contain weakened or dead parts of a virus or bacterium.

Novavax vaccine – Uses a different technology to the Pfizer and AstraZeneca vaccines. It’s a “protein subunit” vaccine; these are vaccines that introduce a part of the virus to the immune system, but don’t contain any live components of the virus.

This vaccine uses a version of the spike protein made in the lab. The spike proteins are assembled into tiny particles called “nanoparticles”.  The aim is to resemble the structure of the coronavirus, however they cannot replicate once injected and the vaccine cannot cause you to get COVID-19.

In order for these subunit vaccines to generate strong protective responses, they need to include molecules that boost your immune system, called “adjuvants”. These adjuvants mimic the way the real virus would activate the immune system, to generate maximum protective immunity.

Novavax includes an adjuvant based on a natural product known as saponin, an extract from the bark of the Chilean soapbark tree.

COVID Vaccine Injection

Vaccine side effects

You may experience minor side effects following vaccination. Most side effects last no more than a couple of days and you will recover without any problems.

Some people will experience more significant flu-like symptoms from the vaccine compared to other common vaccinations, and may need time away from normal activities.

For the Pfizer vaccine, these symptoms are more common after the second dose. For the AstraZeneca vaccine, these symptoms are more common after the first dose.

Current Advice on which available vaccine to use

There has been a link between the AstraZeneca vaccine and a syndrome called thrombosis in combination with thrombocytopenia. This is an extremely rare blood clotting syndrome. It is very serious and can cause long-term disability and death.

The COVID-19 vaccine by Pfizer is preferred over the COVID-19 vaccine by AstraZeneca in adults aged under 50 years.

This recommendation is based on:

  • the increasing risk of severe outcomes from COVID-19 in older adults (and hence a higher benefit from vaccination), and
  • a potentially increased risk of thrombosis with thrombocytopenia following AstraZeneca vaccine in those under 50 years.

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Next week

The Covid Vaccines – What Does It Do? Part 2