Australian Study Adds to Evidence That COVID Vaccines Cause Myocarditis

A new study by Australian researchers concluded myocarditis following COVID-19 vaccination tended to be clinically mild, but the condition affected young men more severely than other groups.

by Brenda Baletti, Ph.D.

A new study by Australian researchers concluded myocarditis following COVID-19 vaccination tended to be clinically mild, but the condition affected young men more severely than other groups, TrialSite News reported.

According to the study, published Monday in the Medical Journal of Australia, most patients with confirmed myocarditis experienced chest pain, had abnormal cardiac imaging results and almost all had high troponin levels — an indicator of heart damage.

“These findings necessitate a careful reevaluation of the risk-benefit analysis for COVID-19 vaccination, particularly in younger populations,” said TrialSite News publisher Daniel O’Connor.

“What the authors and much of medical establishments across the developed world avoid, even mild myocarditis can have long-term cardiovascular consequences, including the potential for chronic cardiac dysfunction and arrhythmias,” according to Trial Site News.

Cardiologist Dr. Peter McCullough told The Defender:

“Myopericarditis is never mild because inflammation and scarring in the heart, no matter how small, can set up a young person for the lifelong risk of heart failure and cardiac arrest. All products that cause heart damage if left on the market should carry a black box warning for myopericarditis as a potential fatal side effect.”

The Centers for Disease Control and Prevention (CDC) states that myocarditis and pericarditis are serious adverse events that can follow COVID-19 vaccination. However, the information is buried on the COVID-19 vaccine safety webpage.

According to the CDC, myocarditis and pericarditis following vaccination are rare and severity can vary.

Evidence obtained through Freedom of Information Act requests and reported by The Defender showed that the CDC has tried to minimize public perception of the risk of myocarditis — the agency even debated whether to make the information public at all.

A study funded by the U.S. Food and Drug Administration and published in September found that 60% of young people who were hospitalized with myocarditis after receiving an mRNA COVID-19 vaccine still showed signs of myocardial injury roughly six months after getting the shot.

As of Dec. 27, 2024, 27,357 cases of myocarditis and pericarditis had been reported to the Vaccine Adverse Event Reporting System (VAERS) in the U.S., with 20,846 cases attributed to Pfizer, 5,952 cases to Moderna and 482 cases to the Johnson & Johnson vaccine.

3 of 4 myocarditis cases occurred in young men within 2 days of vaccination

The Australian study analyzed cases of suspected myocarditis following the COVID-19 vaccine in Victoria, Australia between Feb. 22, 2021, and Sept. 30, 2022.

The cases were reported to the Surveillance of Adverse Events Following Vaccination in the Community (SAEFVIC) system, Victoria’s voluntary reporting system for adverse events related to vaccines.

Of 454 SAEFVIC reports of suspected COVID-19 vaccine-associated myocarditis, the researchers classified 206 as confirmed cases. They analyzed the clinical presentations, diagnostic findings and demographic variations like age and sex from those cases to understand how myocarditis from vaccines presents clinically.

Overall they estimated the myocarditis case rate to be 2.1 per 100,000 vaccine doses for dose 1 and 5.6 per 100,000 vaccine doses for dose 2 for all brands of the COVID-19 vaccine.

The researchers found the median age of those who suffered myocarditis was 21, and 63% of the cases occurred in people age 24 or younger. Three of four cases of COVID-19 vaccine-associated myocarditis occurred in young men. The median time from vaccination to symptom onset was two days.

They speculated that the higher frequency of myocarditis in young men might relate to the pro-inflammatory effect of testosterone or other age-related hormonal issues. However, they also noted that females may be underdiagnosed because they have different and more subtle symptoms, such as palpitations and nausea.

Ninety-eight percent of the cases followed mRNA COVID-19 vaccines, with most of those linked to the Pfizer vaccine, which was more widely distributed in Australia. The remaining 2% of cases followed the AstraZeneca vaccine. Sixty-seven percent of the cases followed the second vaccine dose.

Nearly all of the patients presented to emergency departments with symptoms. Of those, 129 were admitted to the hospital and five required intensive care. The researchers also reported one death.

Australia’s Therapeutic Goods Administration Vaccine Safety Investigation Group investigated that death and concluded that the vaccine — Moderna’s Spikevax — “may have contributed to the development of myocarditis,” but that other factors were also at play in the death, the authors noted.

Just over half of the patients had electrocardiographic abnormalities, more common among males than females. Of the 206 cases, 205 had high troponin levels and the median level increase was also higher in males.

The researchers found that cardiac MRI abnormalities appeared only in patients with a troponin level increase greater than threefold. They concluded that a threefold troponin increase could be used as a risk threshold for clinicians — flagging the need for particular treatment actions — particularly in clinical settings where practitioners don’t have access to cardiac MRIs.

It also may be an important marker of myocyte, or muscle cell, damage.

The authors acknowledged that the study was limited by possible reporting biases inherent in surveillance data, and incomplete clinical data in some cases.

The Australian researchers called for investigation into the longer-term clinical outcomes of COVID-19 vaccine-associated myocarditis, including the persistence of symptoms, possible cardiac abnormalities over time, and long-term complications from the heart injury.