TGA updates post-COVID vaccine myocarditis rates

Matt Woodley

19/11/2021 4:18:32 PM

As many of Australia’s remaining vaccine-hesitant patients express concerns over rare side effects associated with mRNA vaccines, the TGA has broken down rates of myocarditis cases following Pfizer doses.

Young boy receiving Pfizer vaccine
Boys aged 12–17 are more likely to develop myocarditis following their second Pfizer dose. (Image: AAP)

This article was updated at 5.50 pm Monday 22 November.
‘I’m worried about the side effects.’
It is a common refrain among Australians who are still reluctant to receive a COVID vaccine, whether due to the extremely rare possibility of blood clots with AstraZeneca, or myocarditis and pericarditis with Pfizer or Moderna.
As fewer doses of AstraZeneca are administered in the latter stages of Australia’s vaccine rollout, hesitant people are increasingly expressing concerns over the mRNA options.
Melbourne’s Sumit Aneja is concerned after someone he knows who had never previously had heart problems developed pericarditis following a vaccine.
‘To me COVID doesn’t present a real danger to my life because I’m a healthy individual, I take care of myself,’ he told Nine Newspapers.
‘It’s a disease, anyone can get it. But if I willingly put something in my body which can cause me harm, I’ll never be able to forgive myself.’
But according to the Therapeutic Goods Administration’s (TGA) latest safety report, the likelihood of developing myocarditis or pericarditis after an mRNA vaccine remains exceedingly rare.
Australia recorded only 28 new cases deemed ‘likely myocarditis’ following mRNA vaccination over the previous week, 10 fewer than the prior seven days, the report found.
The updated figures, current as of 14 November, mean there have been 329 reports of likely myocarditis from approximately 23.4 million doses of Pfizer and 978,000 Moderna doses.
A further 592 cases have been identified as ‘suspected myocarditis’, including 116 in children aged 12–17, while there have been 1370 cases of suspected pericarditis only.  
The youngest case classified as likely myocarditis to date was 12 years old.
Being infected with COVID-19 itself is ‘associated with a substantially higher risk of myocarditis and other cardiac complications compared to the COVID vaccines’.
The relatively low number of Moderna doses administered in Australia to date means the TGA is unable to provide a reliable estimated rate of myocarditis following vaccination. However, it has provided the below table in relation Pfizer, which breaks down the rates between age groups and sexes.
Rates of myocarditis cases following Pfizer

Age (years) All doses Second doses  
Rate per 100,000 doses Rate per 100,000 doses  
  Male Female Male Female  
12–17 5.6 1.3 8.5 2.3  
18–29 3.1 1.2 3.7 1.5  
30–39 1.4 0.6 1.5 0.6  
40–49 0.7 0.8 1.2 1.1  
50–59 0.4 0.4 0.1 0.4  
60–69 0.0 0.4 0.0 0.0  
70+ 0.0 0.2 0.0 0.0  
All ages 2.1 0.9 2.7 1.1  
The table shows suspected myocarditis following a second dose of Pfizer occurs at a rate of 8.5 cases per 100,000 in boys aged 12–17, more than three times higher than the overall rate among all males of 2.7 per 100,000.
Boys aged 12–17 are also more than twice as likely to develop suspected myocarditis following a first Pfizer dose (5.6 per 100,000) than the general male population. Both of the 12–17 age group figures are an increase on the rates contained in the most previous TGA safety report (5.2 and 7.1 cases per 100,000 first and second doses, respectively).
Importantly, the TGA states that while the rates contained in the table include cases of likely myocarditis that occurred after vaccination, they may not necessarily be vaccine-related and are still lower than myocarditis rates in people infected with COVID-19.
Additionally, the number of younger people vaccinated is still relatively low in Australia, so estimated reporting rates are based on limited data.
According to the TGA, of the cases classified as likely myocarditis, most patients experienced symptoms within three days of vaccination. Around half were admitted to hospital, including 11 who were treated in intensive care.
Most patients treated in hospital were discharged within four days and there have been no vaccine-related fatalities for either Pfizer or Moderna in Australia.
Nine people are suspected to have died following a dose of the AstraZeneca vaccine, including eight due to thrombosis with thrombocytopaenia (TTS) and one case of immune thrombocytopaenia (ITP).
However, the number of TTS cases has reduced substantially in recent months alongside reduced utilisation of the AstraZeneca vaccine, with the most recent deaths occurring at the end of August.
Only three new probable cases of TTS were identified in the past week, all men aged 62–78, bringing the overall number of confirmed or possible cases to 163 from 13.4 million doses.
As well as TTS and ITP, the TGA is also monitoring reports of Guillain-Barre syndrome (GBS) following vaccination with AstraZeneca.
A while clear link between the vaccine and GBS has not been established, the TGA has received 148 reports of people developing the syndrome following vaccination, at a rate of about one in every 100,000 people.
Overall, nearly 81,000 adverse events have been reported to the TGA since the beginning of the rollout at a rate of about 2.1 per 100,000. The vast majority of these have been injection-site reactions (such as a sore arm) and more general symptoms, like headache, muscle pain, fever and chills.
Around 10,000 potential claims related to adverse reactions have been registered with the Federal Government’s no-fault indemnity scheme since September.
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Dr Angela Catanzariti   23/11/2021 6:31:00 AM

As a Dr I'm tired of hearing the TGA label potentially serious side effects as 'possible' or 'likely' and stating that these side effects may not be linked to the vaccine despite occurring post vaccination! As doctors we need to provide our patients with the truth, be transparent about potential risks and allow people to make an educated decision. The TGA needs to grow up!

Dr Brendan Leslie   23/11/2021 8:04:34 AM

It’s more a case of doctors needing to become more familiar with science rather than the TGA needing to ‘grow up’. It sounds like you’re suggesting that because I got a pimple on my cheek following vaccination the vaccine must have caused it. This is inductive, non scientific reasoning.

Deductive, scientific reasoning, requires us to give the vaccine to one group and not another, and compare rates of side effects in both groups.

Unfortunately the words ‘possible’ and ‘probable’ are necessary because medicine is not black and white- our jobs would be easy if this were not the case.

Dr John Malios   23/11/2021 10:02:43 AM

It is pleasing that the TGA has made a statement regarding the risk of myocarditis for teenagers with both the Pfizer and the Moderna vaccine. What is concerning however is the absence of any comment regarding the concerns regarding the use of Moderna for teenagers and the actions taken by those countries. Instead, the TGA states that because of the small number of Moderna administered in Australia the data is not sufficient for an opinion. However, there is data and responses to data from overseas. The Nordic countries including Sweden Finland Iceland have all suspended the use of the Moderna in teenagers. The FDA in the USA has also suspended the use of the Moderna in teenagers as has also occurred in Japan. Canada has also raised concerns. The UK is administering one dose of Pfizer to teenagers. Germany and France have also withdrawn Moderna for younger individuals Therefore, there is ample evidence of information from reliable sources for the TGA to comment. There is a difference between the Pfizer and Moderna in the antigenicity component which may explain the different response in young healthy immune systems
Even a very small risk of myocarditis in a healthy teenager should be considered seriously “first do no harm” In my opinion there is a need for the TGA to comment on this and provide explanation as to why in Australia we are not responding to the overseas data and responses

Dr Janice Faye Sheringham   23/11/2021 10:43:49 AM

Then there is the issue, often raised in overseas comments on this, that the most common of these reactions is actually pericarditis without any significant myocardial involvement! As such, pericarditis carries none of the longer term risks of myocarditis, so it is important on all fronts to get the diagnosis correct! Those cases with only small rises in enzymes and troponin but significant chest pain with pleuritic and positional variations should not be labelled as myocarditis when the principal underlying pathology doesn’t involve the myocardium. The distinction is important and many cardiologists in USA are stressing this point, no matter how quickly they recover.

Dr Peter James Strickland   23/11/2021 12:02:41 PM

My distinct clinical acumen tells me that Covid19 can cause a vasculitis and lead to coronary vasculitis, pulmonary vasculitis and cerebral vasculitis as the probable cause of any heart, lung, thrombosis or brain effects (as known now) in hospital patients in particular. The important thing is how the natural disease pathology and the rare side- effect pathology statistics compare. Is myocarditis diagnosis clinical or pathological (by biopsy), and if the latter what do the vessels look like under the microscope? Talking about any rare and unproven absolute side-effect causes more anxiety than anything, and needs to cease, and rather convince everyone to get vaccinated, and get back to normality in society, and sensible and rational disease management that always exists with some side -effects.

Dr Ian   23/11/2021 12:28:49 PM

Reading all the above we can hope that the Novovax protein based vaccine can arrive soon if it safer
One problem which is severe is the next vaccine for a patient that gets myocarditis .
The one in 10,000 is too high and some had to be treated in intensive care .

Dr John Malios   23/11/2021 12:53:24 PM

This is not a anti vax message I fully support the Covid vaccination programme and have encouraged vaccination for all ( even in a newspaper article for a ethnic group ) The issue is the use of Moderna in the younger age group which has been paused or ceased in more than one country and no comment from the TGA regarding this

Dr Irandani Anandi Ranasinghe-Markus   23/11/2021 8:28:06 PM

It will also be most useful to see the above table ‘Rates of myocarditis cases following Pfizer’ include the general incidence of myocarditis in those age groups to put things in perspective. Also include myocarditis as a complication of COVID. Good point about overseas Moderna statistics.

Dr Hendrik Smit   24/11/2021 3:09:17 PM

Till one's own child ( the talented sports person ) is the one in a 10........ who get myocarditis from the vaccine ....... what will one tell that child ? Was it for his own good and for the good of the community that they now has long term heart damage ? We often find it easy to run "blind" till things hit home.

Dr Julia   24/11/2021 8:44:26 PM

Why has TGA not published data for post AZ COVID vaccine pericarditis and myocarditis? These are recognised adverse reaction in published OS data, eg UK