About the AstraZeneca COVID-19 vaccine

The AstraZeneca vaccine has been provisionally approved by the Therapeutic Goods Administration (TGA) for people 18 years and older. Find out more about the vaccine and who it is recommended for.

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COVID-19 vaccination resources

COVID-19 vaccination – Patient resources

This collection contains resources for patients receiving a COVID-19 vaccination.

ATAGI advice on COVID-19 AstraZeneca vaccine

The Australian Technical Advisory Group on Immunisation (ATAGI) recommends the COVID-19 vaccine by Pfizer (Comirnaty) is preferred in adults aged under 60 years.
In people 60 years and over, ATAGI continue to advise that the benefits of vaccination with the AstraZeneca vaccine outweigh the risks associated with vaccination.
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
  • the increased risk of thrombosis with thrombocytopenia following AstraZeneca vaccine in those under 60 years.

There appears to be a small risk of TTS in people 60 years and over, but this risk appears to be lower than in younger people. Cases overseas have been reported at all ages.

If you are under 60 years of age and have already had your first dose of the AstraZeneca vaccine, and did not experience abnormal side effects, ATAGI recommends you still receive your second AstraZeneca dose. This will provide you with greater coverage against severe illness from COVID-19.

People who are considering vaccination with AstraZeneca COVID-19 vaccine should be aware of this potential complication as part of providing informed consent.

The COVID-19 AstraZeneca vaccine can be used in adults aged under 60 years where the benefits clearly outweigh the risk for that individual and the person has made an informed decision based on an understanding of the risks and benefits.

If you are aged 18-59 years of age, you can choose to receive the AstraZeneca vaccine:

  • following an appropriate assessment of suitability by a qualified health professional; and
  • if you provide verbal or written consent.

Advice from ATAGI about the use of the AstraZeneca vaccine in the context of an outbreak of the COVID-19 delta strain.

Given the heightened risk of people becoming infected, ATAGI’s advice in responding to such an outbreak of the COVID-19 delta strain is that anyone who has received an AstraZeneca vaccine more than 4 weeks ago should contact their vaccine provider to arrange their second dose as soon as possible.

ATAGI has also reinforced its earlier advice that the benefits to people aged 60 or over of being vaccinated with the AstraZeneca vaccine strongly outweigh the risks – and that vaccination is essential for this group in the context of an outbreak.

Noting the current constrained supply of the Pfizer vaccine, ATAGI also recommends adults under the age of 60 who do not have immediate access to the Pfizer vaccine should consider the benefits and risks of earlier protection through the AstraZeneca vaccine.

This recommendation is in the context of an outbreak increasing the risk of people contracting COVID-19 – and hence the increased benefit vaccination provides.

Receiving the AstraZeneca vaccine

Two doses of the Astra/Zeneca vaccine are required.

From a regulatory perspective, the TGA has reviewed all the available evidence and determined that the AstraZeneca vaccine can be safely administered 4-12 weeks apart.

People who have had the first dose of the COVID-19 AstraZeneca vaccine without any serious adverse effects should have the second dose. This includes under 60 years.

Risks of vaccination

As with any vaccine, you may have some temporary side effects after receiving a COVID-19 vaccine. Common side effects after COVID-19 Vaccine AstraZeneca include:

  • injection site pain or tenderness
  • tiredness
  • headache
  • muscle pain
  • fever and chills

Most side effects are mild and temporary, going away within 1-2 days. As with any medicine or vaccine, there may be rare and/or unknown side effects.

Thrombosis with thrombocytopenia syndrome (TTS)

The COVID-19 Vaccine AstraZeneca appears to be associated with a rare side effect called thrombosis with thrombocytopenia syndrome (TTS).

What is TTS?

TTS involves blood clots (thrombosis) and low levels of blood platelets (thrombocytopenia), In Australia symptoms of TTS have occurred between 4 and 42 days post-vaccination. The blood clots can occur in different parts of the body, such as the brain (called cerebral venous sinus thrombosis or CVST) or in the abdomen. The mechanism that causes TTS is not fully understood, but it appears similar to heparin-induced thrombocytopenia (or HIT), a rare reaction to heparin treatment.

How common is TTS?

Overall there is a very low chance of this side effect. But the rate is estimated to be higher in those under 60 years of age. Recent estimates of risk associated with first does of COVID-19 Vaccine AstraZeneca are listed in the table below:

Age Estimated risk of TTS per 100,000
AstraZeneca vaccine doses (first dose)

<50 years


50-59 years


60-69 years


70-79 years


80+ years


  • *as at June 2021

What symptoms does thrombosis with thrombocytopenia syndrome usually cause?

TTS is rare and occurs around 4-42 days after vaccination. Symptoms can include abdominal pain and/or severe headache that does not settle with pain relief. More information about TTS symptoms is in the patient information sheet on AstraZeneca COVID-19 vaccine and thrombosis with thrombocytopenia syndrome. People should seek medical attention immediately if they experience these symptoms.

Are any groups more at risk of TTS?

The rate of TTS reported in Australia and overseas is higher in younger adults and it may be more common in women. However cases have also been reported in men and in older people.

It is not yet clear if women are at higher risk. More women than men have been vaccinated in some countries as they are a large proportion of frontline healthcare workers and have been prioritised for vaccination.
Based on current information, we do not know if there are any pre-existing medical conditions that may contribute to developing TTS or make it worse if it occurs.

Advice for people who have had blood clots in the past

Comirnaty (Pfizer) vaccine is preferred in people who have a past history of cerebral venous sinus thrombosis or heparin-induced thrombocytopenia, given the similarities between these conditions at TTS. You can still have the AstraZeneca vaccine if you have:

  • had other types of blood clots in the past, such as deep vein thrombosis (DVT) or pulmonary embolism (PE)
  • other risk factors for blood clots.

There is no evidence that people who have had a past history of other types of blood clots have an increased risk of TTS. The overall rate of blood clots has not risen in countries which have extensively used the AstraZeneca vaccine.

Blood clots occur commonly in the population, and not all blood clots that occur after AstraZeneca COVID-19 will be caused by the vaccine. If you develop a blood clot after vaccination, your doctor can do blood tests to determine the cause.

covid-19 video – Explainer video on TTS
Read transcript

The vaccines currently used in Australia have  been rigorously tested for safety and are highly effective.

A very rare but serious new side effect has emerged with the AstraZeneca vaccine - a blood clotting syndrome called thrombosis in combination with thrombocytopenia, or TTS.

TTS is extremely rare. It's also new, and was not found in the clinical trials for the AstraZeneca vaccine.  

Evidence shows that TTS is less likely in older adults. And they have a higher risk of getting very sick if they get COVID-19.

That is why  the vaccine preferred for you has changed, depending on your age. COVID-19 can spread quickly and widely and has resulted in the deaths of  millions of people worldwide.

Vaccination is  the most effective way to protect ourselves and our community against COVID-19.  To learn more visit health.gov.au

Advice for people who have had their first dose of AstraZeneca vaccine

Almost all of the cases of TTS reported to date have occurred after the first dose of the vaccine. People who have had their first dose without any serious side effects can be confident in getting their second dose.

Advice for people with weakened immune systems (immunocompromise)

People with immunocompromise includes those who have a medical condition or are taking medications that weaken their immune system. People with immunocompromise, including those living with HIV, have a higher risk of severe illness from COVID-19, including a higher risk of severe illness and death.

The Australian Government strongly recommends people with immunocompromise receive a COVID-19 vaccine. COVID-19 Vaccine AstraZeneca does not behave like a ‘live vaccine’. The adenovirus carrier has been modified so that it cannot replicate or spread to other cells, and it cannot cause infection. It is safe in people with immunocompromise.

Clinical trials for COVID-19 Vaccine AstraZeneca did not include people with immunocompromise, but many people with such conditions have now been vaccinated worldwide. A clinical trial is being conducted of COVID-19 Vaccine AstraZeneca given to people with stable HIV infection, with results expected in a few months.

We do not know if COVID-19 Vaccine AstraZeneca is as effective in people with immunocompromise compared with the rest of the population. It is possible that it might be less effective, and so it is important to continue other preventative measures such as physical distancing after vaccination.

For more information on use of the vaccine in immunocompromised see: COVID-19 vaccination decision guide for people with immunocompromise.

Advice if you are pregnant or breastfeeding

If you are pregnant, breastfeeding, or planning pregnancy it is preferable for you to have the Pfizer COVID-19 vaccine. This is the preferred vaccine in young adults. However, you can still have the COVID-19 Vaccine AstraZeneca if the benefits of vaccination outweigh the risks for you.

Read more about COVID-19 vaccines if you are pregnant or breastfeeding.

Advice for people with a history of COVID-19

If you have ever had COVID-19 in the past, tell your immunisation provider. Your provider may advise to wait for up to 6 months after recovery before having a COVID-19 vaccine. If you have ongoing illness from COVID-19, discuss the best timing of vaccination with your treating doctor. Either COVID-19 vaccine brand can be used in people with a past history of COVID-19

COVID-19 vaccine AstraZeneca and children

COVID-19 Vaccine AstraZeneca has only been provisionally approved for use in people aged 18 years or older, and cannot be given to younger people. The risk of COVID-19, especially severe disease, in children is lower than in older adolescents and adults.

Vaccine safety and reporting adverse events

The Therapeutic Goods Administration (TGA) assesses all vaccines in Australia. This ensures that in order for a vaccine to be approved it is safe, effective and manufactured to a very high quality standard. A description of the process for approval of COVID-19 vaccines is available on the TGA website. The safety of COVID-19 vaccines will be monitored continuously throughout the COVID-19 vaccination program. Suspected side effects can be reported to your vaccination provider or other healthcare professional. They will then make a formal report on your behalf to your state or territory health department or directly to the Therapeutic Goods Administration (TGA). If you would prefer to report it yourself, please visit the TGA website for information on how to report suspected side effects associated with COVID-19 vaccines.

More information

COVID-19 vaccination – Provider resources

Read and download clinical guidance and other resources for COVID-19 vaccines provided by the Australian Technical Advisory Group on Immunisation (ATAGI).

Find out more about the provisional approval of the AstraZeneca COVID-19 vaccine.

National coronavirus and COVID-19 vaccine helpline

If you need information about COVID-19, COVID-19 vaccines or help with the COVIDSafe app, call 1800 020 080. If you need assistance with booking a COVID-19 vaccine appointment, please note the call centre is unable to book appointments on your behalf.

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Last updated: 
14 July 2021

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