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COVID-19 vaccine weekly safety report - 23-09-2021

Vaccination against COVID-19 is the most effective way to reduce deaths and severe illness from infection. Millions of people have received COVID-19 vaccines under the most intense safety monitoring ever conducted in Australia. 

Three COVID-19 vaccines are currently in use in Australia – Vaxzevria (AstraZeneca), Comirnaty (Pfizer) and Spikevax (Moderna). To be registered for use, these vaccines have met the TGA’s high standards for quality, safety and effectiveness.

Like all medicines, COVID-19 vaccines may have some side effects (also known as adverse events). The overwhelming majority of these side effects are mild and resolve within a few days. More serious side effects can occur after vaccination but are very rare.

The TGA closely monitors reports of suspected side effects to the COVID-19 vaccines. In the next few weeks, we will start receiving reports for the Spikevax (Moderna) vaccine as it is rolled out in Australia. We will provide regular updates on its safety in this report, along with the Vaxzevria (AstraZeneca) and Comirnaty (Pfizer) vaccines. Find out how the TGA identifies and responds to a safety concern

Importantly, suspected adverse events reported to the TGA are often not caused by the vaccines. Learn more about causality and the TGA’s COVID-19 vaccine safety monitoring and reporting activities. 

Report a suspected side effect.


  • The protective benefits of vaccination against COVID-19 far outweigh the potential risks of vaccination. 

  • To 19 September 2021, approximately 24.8 million vaccine doses have been given in Australia – 15.1 million first doses and 9.7 million second doses.

  • The most frequently reported side effects suspected to be associated with the vaccines reflect what was seen in the clinical trials. They include injection-site reactions such as a sore arm, and more general symptoms such as headache, muscle pain, fever and chills.

  • We are closely monitoring rare reports of blood clots with low blood platelets (also called thrombosis with thrombocytopenia syndrome or TTS) linked to Vaxzevria (AstraZeneca). 

  • In the last week, an additional 7 reports of blood clots and low blood platelets have been assessed as confirmed or probable TTS. None of these cases were fatal.

  • We also continue to carefully monitor reports of suspected myocarditis following the Comirnaty (Pfizer) vaccine, particularly in the younger age groups.

Reported side effects for COVID-19 vaccines

Gathering reports of adverse events following immunisation (AEFI) is just the first step in determining whether the effect is related to the vaccine and whether a significant safety issue is involved. Learn more about how the TGA identifies and responds to safety issues

The most frequently reported side effects suspected to be associated with the vaccines include injection-site reactions such as a sore arm, and more general symptoms such as headache, muscle pain, fever and chills.

Large scale vaccination means that coincidentally some people will experience a new illness or die within a few days or weeks of vaccination. 

The TGA reviews all deaths reported in people who have been vaccinated. As the number of vaccinated people has increased, so has reporting of fatal events with a coincidental association with vaccination. This does not indicate a link between vaccination and the fatalities reported. Review of individual reports and patterns of reporting does not suggest the vaccines played a role in these deaths.

Since the beginning of the vaccine rollout to 19 September 2021, approximately 24.8 million doses of COVID-19 vaccines have been given. So far, the TGA has found that 9 reports of deaths were linked to immunisation from 556 reports received and reviewed.  The overwhelming majority of deaths reported to the TGA following vaccination occurred in people aged 65 years and older.  The deaths linked to immunisation occurred after the first dose of Vaxzevria (AstraZeneca) – 8 were TTS cases and one was a case of immune thrombocytopenia (ITP).

Total adverse event reports to 19 September 2021

Reporting rate per 1000 doses
Total AEFI reports received
Total doses administered
Total reports for Vaxzevria
Total reports for Comirnaty
Total reports for brand not specified

Reporting rates per 1000 doses by jurisdiction

Australian Capital Territory
New South Wales
Northern Territory
South Australia
Western Australia

Interpreting information on vaccine adverse event reports

The Database of Adverse Event Notifications (DAEN) is our publicly available adverse event database. We have recently upgraded the DAEN and are in the process of restoring full functionality. We apologise for any inconvenience. Importantly, these issues have not affected our ability to receive and analyse adverse event reports.

We are aware of false claims that have been circulating based on misinterpretation of information published in the DAEN. Reports are entered into the database without being assessed to determine if they are caused by the vaccine. We encourage people to report suspected side effects, even if there is only a small chance that the vaccine caused them. For this reason, publication of a report in the DAEN does not mean that the vaccine caused the adverse event, but simply reflects the observations of the person who reported the event. 

In some states and territories, the reporting of specific events, such as death, that occur closely following a vaccination is mandatory for health professionals. For this reason, the number of adverse events and deaths reported in the DAEN is not an indication of the safety of the vaccines. Expert review and investigation are needed to determine which events were caused by the vaccine. The outcomes of our analysis of adverse event reports are communicated in this report each week.

When looking for information about COVID-19 vaccines, consider whether the source is credible. Websites such as ‘COVID vaccines – is it true?’ and RMIT ABC Fact Check can help to address false claims and misleading rumours. Other reliable resources are listed at the end of this report.

Vaxzevria (AstraZeneca) vaccine

To 19 September 2021, approximately 11.3 million doses of Vaxzevria (AstraZeneca) have been administered in Australia. The reports of suspected side effects we receive for this vaccine are consistent with what has been observed in the clinical trials and by other medicine regulators overseas. Most side effects resolve within a few days.

Thrombosis with thrombocytopenia syndrome (TTS)

We are closely monitoring rare reports of blood clots with low blood platelets (also called thrombosis with thrombocytopenia syndrome or TTS) linked to Vaxzevria (AstraZeneca). 

Early detection of TTS may help to prevent more serious complications developing. Guidance for health professionals is now available which outlines when to suspect TTS, initial tests that can be performed in primary care and when to refer people for emergency care. Patients presenting with low platelets and a headache should be thoroughly investigated for blood clots in the brain, including careful review of imaging results to identify early, small clots. The Royal Australian and New Zealand College of Radiologists have published imaging recommendations for patients with suspected TTS.

People should seek immediate medical attention if they develop any of the following symptoms after vaccination:

  • severe or persistent headache, blurred vision, confusion or seizures

  • shortness of breath, chest pain, leg swelling or persistent abdominal pain

  • unusual skin bruising and/or pinpoint round spots beyond the site of vaccination.

The most common time period for onset of TTS symptoms is 4–30 days after vaccination.

To date, there have been 141 cases of TTS assessed as related to Vaxzevria (AstraZeneca) from approximately 11.3 million vaccine doses. These cases most often occurred about 2 weeks after vaccination. The risk of TTS after a second dose appears to be much lower than after the first dose. Women in younger age groups seem to be slightly more likely to develop clots in unusual locations, such as the brain or abdomen, which have more serious outcomes. Eight people have died as a result of TTS – 6 of these were women. In Australia, the risk of dying from TTS after vaccination is approximately 1 in a million (people receiving a first dose).

While TTS is very rare, some people may have concerns that they can discuss with their doctor. ‘Weighing up the potential benefits against risk of harm from COVID-19 Vaccine AstraZeneca’ includes information to help people make informed decisions about vaccination.

Details of TTS cases to date

Since last week’s report, a further 7 reports of blood clots and low blood platelets have been assessed as confirmed or probable TTS likely to be linked to the first dose of Vaxzevria (AstraZeneca). Two of the new cases of TTS reported this week were in individuals aged under 60 years (Table 1). We continue to closely monitor cases of TTS as Vaxzevria (AstraZeneca) is now being used more frequently in people aged under 60 years. To date, we have not observed a significant change in the rate of TTS in people aged 50-59 years. There has been a trend for the rate to decrease in people under 50-years, but due to the low number of cases this is not statistically significant. 

Table 1: Newly confirmed and probable TTS cases for the week of 17-23 September 2021‡

New confirmed TTS

New probable TTS

Two new cases:

  • 34 and 79-year-old men from NSW

Five new cases:

  • 54, 66, 71, 74 and 77-year-old men from NSW

As previously reported, the TGA determines whether a report is likely to represent TTS by assessing cases against accepted criteria established by the UK’s Medicines and Healthcare products Regulatory Agency. 

This takes the total Australian reports assessed as TTS following Vaxzevria (AstraZeneca) to 141 cases (77 confirmed, 64 probable) from approximately 11.3 million vaccine doses.

To date, 13 cases of TTS have occurred after the second dose. Eleven cases have been classified as probable TTS, with 2 cases meeting the criteria for confirmed TTS. All cases have occurred in individuals older than 50 years, with 11 of the cases in people over 60 years of age. Eleven of the patients had clots in common locations, such as the lungs or legs, with only 2 cases classified as Tier 1 (see below). The information available to us indicates that only one of these patients required treatment in the intensive care unit, and 9 individuals have been discharged from hospital. Our preliminary analysis is consistent with overseas investigations which have shown that the risk of TTS after the second dose is extremely low (for example, 1.9 cases per million based on data from the UK). 

When assessed against the criteria used by the US Centers for Disease Control and Prevention (CDC), fewer than half of the cases reported to the TGA are classified as Tier 1 cases which tend to have more serious outcomes. Tier 1 cases involve clots in an unusual location, such as the brain or abdomen (Table 2). Australian data indicates that patients aged under 50 years of age are more likely to be classified as Tier 1 and/or require treatment in intensive care. However, more than one third of these younger patients have not required treatment in intensive care. 

Table 2: Total confirmed and probable TTS cases to date by age and CDC classification


Total cases

Reports per 

100,000 doses‡

CDC classification†

Tier 1

Tier 2

Not classified

<30 years



(<50 years)





































All ages


(64 men,

71 women)



(19 men, 

34 women)


(25 men, 

16 women)


(26 men, 

21 women)

‡ Rates of TTS are calculated based on first doses of the Vaxzevria (AstraZeneca) vaccine as of 19 August to account for the time to onset of TTS. These rates are estimates of risk based on small numbers of cases so far.  

† The US CDC classification is defined as:

  • Tier 1 = clots in an unusual location (such as the brain or abdomen) and a low platelet count with or without antibodies that activate platelets (anti-PF4 antibodies)

  • Tier 2 = clots found in common locations (such as the leg or lungs) and a low platelet count and anti-PF4 antibodies

  • Not classified = case does not meet the criteria for Tier 1 or Tier 2 (for example clots in common locations with low platelet count but no evidence of anti-PF4 antibodies).

Cases have most often occurred about 2-3 weeks after vaccination, although the time to onset (or diagnosis) has ranged from one to 83 days (Table 3). 

Table 3: Time to onset, treatment and outcomes for TTS cases*

Time to onset/ diagnosis (days)

Median (range)

18 (1-83)

Treated in ICU

At any point







In hospital 




*Data is based on the most recent medical information available to the TGA

Other safety signals with Vaxzevria (AstraZeneca)

Guillain-Barre Syndrome (GBS)

GBS is a rare immune disorder affecting the nerves and can result in pain, numbness, muscle weakness and difficulty walking. It has been associated with COVID-19 infection as well as other infectious diseases. Following rigorous investigations by the TGA and other international drug regulators, a clear link between GBS and Vaxzevria (AstraZeneca) has not been established. However as a precautionary measure, a warning statement about GBS has been added to the Product Information in response to rare cases following vaccination.

To 19 September 2021, the TGA has received 118 reports of suspected GBS occurring after vaccination with Vaxzevria (AstraZeneca). These cases will be considered as part of our ongoing monitoring of this safety signal. It is expected that some suspected cases may not be related to vaccination, as GBS can also be caused by other common causes of GBS, such as viral infections and some types of gastroenteritis. 

We encourage people to seek medical attention if they experience symptoms that could suggest GBS as early medical care can reduce severity and improve outcomes. Symptoms to look out for include weakness and paralysis in the hands or feet that can progress to the chest and face over a few days or weeks. These tend to affect both sides of the body.

Immune thrombocytopenia (ITP)

The TGA continues to monitor and investigate reports of suspected ITP, a type of thrombocytopenia or low platelet count. We will communicate the outcomes of this investigation, including any regulatory actions, when it is complete. 

To 19 September 2021, the TGA has received 77 reports of suspected ITP following vaccination. These patients had an extremely low platelet count, and signs of thrombocytopenia which may include unusual bruising, a nosebleed and/or blood blisters in the mouth. Their symptoms occurred in a timeframe that suggested they could be linked to vaccination and no other obvious cause was identified based on the information provided to TGA. Apart from one fatal case that was assessed by an expert Vaccine Safety Investigation Group as being likely to be vaccine related, suspected cases of ITP have not been definitively linked to vaccination.

ITP can occur when the immune system is activated, for example by a viral infection or vaccination, and mistakenly destroys platelets which help blood to clot. In many cases it is mild with up to a third of people having no symptoms at all, or only minor bruising. However, about 5% develop severe bleeding. 

We encourage people to seek medical attention if they experience signs and symptoms that could suggest ITP, such as unusual skin bruising or clusters of small red or purple spots that do not lose their colour when pressed. Unusual bleeding is another sign, for example bleeding from the nose or mouth that is hard to stop, or blood in the urine or stools.

Up-to-date information about the expected side effects of Vaxzevria (AstraZeneca) can be found in the Consumer Medicine Information (for consumers) and Product Information (for health professionals).

Comirnaty (Pfizer) vaccine

To 19 September 2021, approximately 13.5 million doses of Comirnaty (Pfizer) have been administered in Australia. The reports of suspected side effects we receive for this vaccine are consistent with what has been observed in the clinical trials and by other medicine regulators overseas. Most side effects resolve within a few days.

The TGA is actively monitoring myocarditis (inflammation of the heart) and pericarditis (inflammation of the membrane around the heart) and continues to work with international regulators on this safety signal. We will provide periodic updates in this report as more information becomes available.

Myocarditis and pericarditis

Myocarditis and pericarditis are rare effects on the heart that typically occur within 10 days of vaccination with the mRNA vaccines Comirnaty (Pfizer) and Spikevax (Moderna). Cases are usually transient and resolve following treatment and rest.

Our previous analysis of myocarditis reports suggests there is a higher-than-expected number of cases in vaccinated compared to unvaccinated individuals, indicating that in rare cases the vaccine may cause myocarditis.  International data indicates that cases are more frequently reported in teenage boys after the second dose. To 19 September, we have received 8 reports of suspected myocarditis in adolescents aged 15-17 years – 7 boys and one girl. Four of the cases occurred after the second dose.  None of these cases had sufficient clinical evidence to be classified as highly likely to be myocarditis (level 1).  There were an additional 12 reports of suspected pericarditis not combined with myocarditis in this age group of which 5 were clinically consistent with pericarditis. We continue to review cases against an internationally accepted case definition for myocarditis to classify how certain it is that these cases reflect myocarditis. More detailed information on our analysis will be published in next week’s report.

Myocarditis and pericarditis have other causes, including viral infections, and in Australia it is estimated that there would normally be one case of myocarditis diagnosed each week in people aged 0-19 years.  We know that myocarditis and pericarditis are much more common with COVID-19 infection and damage to the heart is frequently severe after infection. The Australian Technical Advisory Group on Immunisation (ATAGI) reaffirms that the protective benefits of the Comirnaty (Pfizer) vaccine outweigh the risk of these rare side effects in all eligible age groups. 

We encourage people to seek medical attention if they experience symptoms that could suggest myocarditis or pericarditis. This includes chest pain, palpitations (irregular heartbeat), fainting or shortness of breath after receiving the vaccine, particularly if they occur within 1–5 days. Initial tests for those presenting with symptoms include ECG, troponin and chest X-ray. ATAGI advises that people who develop myocarditis or pericarditis attributed to their first dose of Comirnaty (Pfizer) should defer further doses of an mRNA COVID-19 vaccine and to discuss this with their treating doctor.

Anxiety-related reactions

A warning about fainting following vaccination has been added to the Product Information for the Comirnaty (Pfizer) vaccine. It states “Syncope (fainting) may occur in association with administration of injectable vaccines. Procedures should be in place to avoid injury from fainting.” 

The TGA has also carried out an investigation of anxiety-related reactions related to this vaccine in response to reporting by consumers to the NPS MedicineWise Adverse Medicine Events line. This investigation considered a range of evidence including Australian and international adverse event data. Examination of the medical literature found that stress-related reactions to immunisation can be more common in younger people. Published evidence also suggests that giving immunisations in a mass vaccination centre can be a contributing factor, particularly when there is a cluster of anxiety-related reactions reported. The risk was consistent with information from clinical trials.

The Consumer Medicines Information and Product Information for the Comirnaty (Pfizer) vaccine already lists stress-related effects of vaccination such as dizziness, fainting, sweating, increased heart rate and anxiety. These side effects are usually mild and get better relatively quickly. If you start to feel any of these symptoms before, during or after receiving your injection, let your doctor, nurse or pharmacist know and make sure you sit or lie down to avoid falling and injuring yourself. 

Up-to-date information about Comirnaty (Pfizer) can be found in the Consumer Medicine Information (for consumers) and Product Information (for health professionals).