With a rapidly changing public health situation and advice updated regularly, it's understandable some people are feeling uncertain about getting a COVID-19 vaccine when available. So we've answered the most common questions.

Australia’s current COVID-19 situation is a sober reminder that we are dealing with an increasingly contagious virus. We may continue to have outbreaks despite our best efforts.

Getting a COVID-19 vaccine is one of the best protections we have right now, for our own health and for the wider population.

But the advice and situation seems to change day-to-day. It’s understandable that some people are feeling uncertain about getting a COVID-19 vaccine (if available).  

So, we’re going to answer some of your common questions about vaccines. We’ll get accurate answers from our experts, so you and your loved ones can make informed decisions about getting vaccinated when the option is available to you. 

So, why get vaccinated? Our Health and Biosecurity Director, Dr Rob Grenfell, provides the science. 

To request a transcript please contact us.

Our Health and Biosecurity Director, Dr Rob Grenfell, answers some of the common questions.

Can you still catch or spread COVID-19 after you get vaccinated? 

This first generation of vaccines are designed to protect you from serious illness or death from COVID-19. If you’re vaccinated, there is a reduced chance you will contract or spread SARS-CoV-2, the virus that causes COVID-19.

The likelihood decreases if you’ve had both doses – but there is still a chance. Fortunately, if you’ve been vaccinated and do develop COVID-19, you should only get a mild case. 

What’s the point of vaccination if you can still catch or spread COVID-19? 

COVID-19 can cause severe disease and death, particularly in older people and those with existing health conditions.  

Even if a low percentage of infected people need medical care, if everyone was infected at once, our hospitals and health systems could quickly be overwhelmed. This has happened in other countries with major outbreaks. 

The point of vaccination is to limit this impact. Both the Pfizer-BioNTech (Pfizer) and Oxford-AstraZeneca (AstraZeneca) vaccines have been shown to reduce your risk of dying or needing to be hospitalised from COVID-19. 

People who are vaccinated have been shown to be less likely to spread the virus too. So, the more people get vaccinated, the more our entire population will be protected. 

Why get vaccinated now? Can I wait? 

As the current outbreaks show, COVID-19 is incredibly contagious. Australia has had one of the most successful responses to controlling the spread of the virus. But we still keep having new cases and hotspots pop up.  

Because COVID-19 is a totally new disease in humans, none of us have any innate immunity to it. So we’re not immune – figuratively and literally – to being overwhelmed by this virus.  

Vaccines are one of the best tools we have to keep ourselves and our loved ones safe from severe disease and death. If a vaccine is available to you, it’s encouraged that you get immunised as soon as possible. 

If everyone else is getting vaccinated, does it matter that much if I don’t? 

People who are vaccinated have a lower risk of getting severely ill or spreading the virus to other people. But the virus may still spread, and if you’re not vaccinated, you will not have any protection against severe illness.   

This is being demonstrated in the UK and the US, where vaccination of high-risk groups has been pretty high, but there are escalating cases of younger people getting sick and being hospitalised with the infection. Getting as many people vaccinated as possible is needed to control this virus.

As with all medicines, we need to carefully consider the risks of vaccinating alongside the risks of not vaccinating. In Australia, the expert panel advising on our vaccine rollout is the Australian Technical Advisory Group on Immunisation (ATAGI).  

It can be hard to keep up with the announcements as the risk-benefit ratio changes with new COVID-19 developments.

For up-to-date information on which vaccines are recommended for different age groups in Australia, look for the latest ATAGI statements in the COVID-19 news section of the Department of Health vaccine website.

Not sure if you fit into a priority group for vaccination right now? Check your eligibility with this tool.

Is the AstraZeneca vaccine less effective than Pfizer? 

Studies have shown both the AstraZeneca and the Pfizer vaccines are highly effective at protecting against severe COVID-19 disease, hospitalisation and death.  

Early discussions about the vaccines were based on clinical trial data because that’s all that was available. But more than 46 million people have received at least one dose of a vaccine in the United Kingdom now, so this gives us real-world data to look at. 

In the real world, Public Health England found that in preventing symptomatic COVID-19: 

  • Two doses of the AstraZeneca vaccine were about 89% effective
  • Two doses of the Pfizer vaccine were about 90% effective

What about the risk of blood clots?

The likelihood of developing the blood clot condition TTS (thrombosis with thrombocytopenia syndrome) after receiving the AstraZeneca vaccine is so low that cases of blood clots were not observed in the preclinical and phased clinical trials.

In Australia, more than 6.8 million doses of the AstraZeneca vaccine have been given so far. Data from the Therapeutic Goods Administration (TGA) shows there have been 93 confirmed or probable cases of the blood clotting from immunisation, sadly with seven deaths. Some people have been hospitalised and most are now recovering.

That puts the rate of getting TTS at 0.00137%, and the death rate from clots even lower – about one in a million.

To put this in perspective, every year in Australia about 30,000 of our 25 million people will develop a blood clot from other conditions – a rate of 0.12%. So, the rate of blood clots in the normal population is almost 100 times greater than the rate of clots related to the AstraZeneca vaccine in Australians.

For further context, in the United Kingdom, 21.2 million doses of AstraZeneca had been given by April 2021. There were 168 cases (representing 0.0008% of all doses) of blood clots, and 32 resulting deaths (0.000151%).

To compare, the risk of dying from COVID-19 is about 2% overall (data from the US Centre for Disease Control prior to the vaccination program).

If Australia were to have an outbreak similar to Europe at the start of this year, modelling from the Department of Health estimates for every 100,000 people over 80 years old, 1.9 would experience the blood clot condition if they had the AstraZeneca vaccine. But without the vaccine, 1239 of those people would be hospitalised from COVID-19, and 733 would die. And this is using data before the more contagious Delta strain became prominent.

Or to look at other age groups:

  • For every 100,000 aged 60-69: 1.4 people would get blood clots, but without a vaccine 324 would be hospitalised and 45 would die.
  • For every 100,000 aged 50-59: 2.7 people would get blood clots, but without a vaccine 208 would be hospitalised and 14 would die.

The COVID-19 disease can also cause blood clots itself. Preliminary studies suggest a person is 100 times more likely to develop a clot from COVID-19, than the general population.

I’ve never got the flu jab and I’ve been fine. Why is COVID-19 different? 

COVID-19 is more contagious than influenza, and it has a higher mortality (death) rate. It’s hard to get proper comparisons because of the different ways these diseases are tracked and reported around the world.

But in a peer-reviewed scientific paper published in The Lancet in December 2020, researchers looked at people hospitalised from COVID-19 and influenza in France.  

The paper found that people in hospital from COVID-19 had a mortality rate of 16.9%, compared to 5.8% for people hospitalised with influenza. 

In other words, COVID-19 is more deadly than the flu. Vaccines are our best protection.  

What if I’ve already had COVID-19? Am I immune?  

If you’ve already had COVID-19, you probably have some immunity against re-infection. But we are seeing that immunity isn’t as long-lasting as we’d hope. And you might still be vulnerable to new variants of the virus.  

We’ve seen that immunity from vaccination is stronger than immunity from the infection itself. And vaccination also appears to reduce the effects of ‘long COVID’.

So, even if someone has previously had COVID-19, vaccination is recommended.   

Can kids get vaccinated right now? 

Vaccines are usually tested in adults first and assessed in children when safety has been proven in adults. This is because children are still developing and growing. COVID-19 has also been a more serious and dangerous disease among older people.

However, the Delta strain has been spreading more easily through children than earlier strains. However, fortunately, children do not seem to get as sick from it. So vaccination of children may be an important part of limiting the virus’ spread. 

Now that the vaccines have been determined to be safe for adults, they are being studied in children. Australia’s medicines regulator, the Therapeutic Good Administration (TGA), will review the use of COVID-19 vaccines to children. This is pending results from further studies with children, which are looking promising. 

The Pfizer vaccine is currently approved in Australia for people aged 16 and over. On 23 July the TGA reviewed trial data and approved the use of Pfizer as safe for children aged 12 to 15 years old.

Next ATAGI will make a recommendation on how to include these children in the national vaccine rollout.

Please note: This information was correct when it was published on 29 July 2021. Please check the Department of Health website for the latest information


  1. Great information, however, I agree to also presenting short, to the point messages, maybe a slogan – get vaccinated, get Australia COVID safe, something like the ‘do the right thing’ litter campaign, ‘Vaccinate don’t hesitate’ these type of messages stick in your mind and have worked before.

    1. Doesn’t Kim’s post just demonstrate that people don’t want – or dont have the understanding/attention span – to read comprehensive information? Let’s have a short, snappy slogan so we can all get back to much more important things like scrolling through our phone to see what the latest z grade celebrity is doing.
      Read the information, digest it, ask questions, ask more questions, let it sink in. You never know, you just might be capable of more comprehension than you realise.

  2. Can we get some information on what is best approach for immune compromised people with a positive blood clot issue in being vaccinated.

    1. Hi Wendy, for people with health concerns, it’s best to speak to your GP directly for advice on getting the AstraZeneca or Pfizer vaccines.

      Team CSIRO

  3. I understand that the vax is not 100% effective, and if I do get Covid, I probably won’t end up in ICU,
    The reason that there is resistance to the jab is summed up in 2 words-
    Blood Clots
    No mention of that in the above article

    1. Agree. Tell both sides of the story. Give me an indication of the risks so I can make an informed choice.

    2. Chance of getting a blood clot from AZ vaccine: 4-6 in a million (that’s a 0.0006% chance at the higher end of getting it for something that could save your life); in 2020 the rate of annual deaths per 100,000 population due to car accidents was 4.4%. You willing to risk popping down to the shops for a loaf of bread for a sandwich (which may also kill you – choking hazard)? Chances are we are all going to get Covid given the virulence of the disease. I personally would like to avoid being seriously ill from it.

    3. Except for the whole section of the article subtitled: “What about the risk of blood clots?”

    4. There is a whole section on blood clots and tts

    5. Go back and look under the heading “What about the risk of blood clots?”.

    6. Yes there is, under this heading.
      What about the risk of blood clots?

    7. Try the section entitled ” What about the risk of blood clots”

    8. Hi Cath – there is a heading in the article ‘What about the risk of blood clots?’ following which is a full explanation of the risk of blood clots. Perhaps you missed it.

    9. excuse me cath but would you please mind looking at the section entitled “what about the risk of blood clots?”

    10. Yes there is look under the heading “What about the risks of blood clots”

    11. https://blog.csiro.au/why-get-vaccinated/ gives details on risks vs benefits of blood clots

  4. Simple and sound advice. Thanks Rob.

    1. I personally met one person who passed away after getting the jab by blot cloths here in Sydney. There was no mention, no condolences, in fact her death went very much under the mat. Why is a person who dies from the vaccine not even worth of a public mention or condolences and one who dies from corona is? I’m having a dilema with the value of life in this kind of situations.

  5. short messages should go out to public in written statement form , Too many are not happy with reading lor hearing long monologues on TV

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