COVID vaccines explained

August 2, 2021

Let’s face it: it’s been a long road, this pandemic. Are you powering on, or just crawling along as best you can?

Either way, for most Australians there’s hope on the horizon. This hope comes in the form of a small vial and 2 jabs in the arm. As our vaccination rates increase, so does our hope that some of the burdens of this pandemic will lift.

What are the vaccines currently available to Australians? And what’s the difference between them?

Will these differences matter for you?

Find out the key facts here.

Types of vaccines

Vaccines are a safe and effective way to help your immune system prepare its defence against deadly germs. We use vaccines to combat the health issues and spread of lots of major illnesses including:

Vaccines are like the training run for the main event.  When you have a vaccine, your immune system will create antibodies, just as it does when it’s exposed to a disease.

However, vaccines contain only modified or weakened forms of germs. They do not cause disease.

At present, we have two vaccines in Australia to combat COVID-19. Both are safe and effective. But not they’re not identical.

Firstly, they have been developed using different technologies: mRNA technology and viral vector technology.

mRNA vaccines

These types of vaccines use messenger-RNA (mRNA, a genetic code). The mRNA provokes cells in your body to produce a COVID-19-specific protein. This is the protein that your immune system will target and attack.

Messenger-RNA vaccines can’t alter or impact your DNA in any way. The Pfizer vaccine is a mRNA vaccine.

Viral vector vaccines

These types of vaccines use a harmless, weakened animal virus. This virus contains the genetic code for a protein unique to COVID-19. Your body will produce antibodies to this protein

The AstraZeneca vaccine is a viral vector vaccine.


You can only get the COVID-19 from a live strain of the coronavirus. COVID-19 vaccines do not contain a live strain of the coronavirus.

So you cannot get COVID-19 from a shot. 

In Australia:

  • the AstraZeneca vaccine is preferred for people over 60 years
  • the Pfizer vaccine is the preferred vaccine for all other people aged 16 to 59.

For more information, see, Which COVID-19 vaccines are available in Australia?

What exactly does the vaccine do?

The research shows that both vaccines protect against COVID-19 symptoms and severe disease after 2 doses.

Vaccines for other diseases may help prevent or reduce the spread (transmission) of viruses.

We don’t yet know if the COVID-19 vaccines reduce or stop the spread of the virus. There is some evidence that it may.

The risks: in context

All vaccines have mild side effects, like a sore arm or mild fever. More serious side effects happen but are extremely rare.

You are most likely aware of the news concerning the AstraZeneca vaccine.

It’s linked to a very rare blood-clotting condition called thrombosis with thrombocytopenia syndrome (TTS). The very low risk of TTS appears to be higher in younger adults, which is why it’s preferred for people aged over 60.

However, if you are aged 18 to 59 you can have the AstraZeneca vaccine if you want to. You need to weigh up the benefits and the risks, and provide informed consent.

If you want to talk to a GP about having the AstraZeneca vaccine, InstantScripts doctors can help.

Talk to an InstantScripts GP about your vaccine options

For further information read this information sheet available on the Department of Health website.


You’ve probably lost count of the number of articles you’ve seen about COVID-19. We sure have.

But not all information is good information.

Make sure you source your information is from trusted sites, such as the World Health Organization (WHO) or government websites. Find out more about sorting fact from fiction.

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