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Professor David Celermajer, cardiologist and Clinical Research Group Leader at the Heart Research Institute, answers some common questions around mRNA COVID-19 vaccines, such as those developed by Pfizer and Moderna, and their potential to cause pericarditis and myocarditis.

While there has been some concern, it is very rare for pericarditis and myocarditis to occur after an mRNA COVID-19 vaccine, with less than three events per 100,000 people. In over 90 per cent of these cases, the disease is easily recoverable with treatment. It’s important to note that these events occur much less frequently than the often severe and life-threatening health complications that can occur with COVID-19 infection.

What are pericarditis and myocarditis?

Pericarditis is inflammation of the two-layered membrane, called the pericardium, that surrounds the heart. The pericardium helps to keep the heart in place and protect it from infection and friction. In pericarditis, the two layers of this membrane become inflamed and can rub against each other as the heart contracts and relaxes, causing pain. Men between 20 and 50 years old are most at risk.

Myocarditis is inflammation of the heart muscle. This inflammation can be mild and cause no short or long term problems OR can be severe and cause enlargement and weakness of the heart, and/or create scar tissue. While myocarditis is a rare cardiovascular condition, it can affect anyone of any age, from infants and children to adults. Myocarditis is usually caused by infection with a virus. It can also sometimes result from a reaction to a medication or therapy.

Pericarditis and myocarditis can occur alone or together.

Are mRNA COVID-19 vaccines linked to pericarditis and myocarditis?

It is very rare for pericarditis and myocarditis to occur after an mRNA COVID-19 vaccine, but experts have confirmed that a small increased risk has been observed in people who have received an mRNA vaccine – such as those developed by Pfizer and Moderna – compared to unvaccinated people. The AstraZeneca COVID-19 vaccine is not associated with an increased risk of pericarditis and myocarditis.

Studies have shown that the risk of myocarditis after the Pfizer COVID-19 vaccine is estimated to cause less than three events of myocarditis per every 100,000 people. For comparison, it is estimated that COVID-19 causes 11 events of myocarditis per every 100,000 people, presenting a much greater risk.

The death rate after COVID-19 infection is around one per cent, whereas the death rate from the mRNA vaccines against COVID-19 is less than one per million.

The rare cases of pericarditis and/or myocarditis after an mRNA COVID-19 vaccine have occurred most commonly in males aged 16–30 years, after the second vaccine dose, with symptoms appearing within one to five days of vaccination. Most of these cases have been mild, and patients have recovered quickly. Longer-term follow-up is ongoing.

Does COVID-19 present a greater risk of pericarditis and myocarditis than the vaccine?

There is a much greater risk of COVID-19 infection causing pericarditis and myocarditis and other cardiac complications, compared to receiving a vaccination. There are overwhelming benefits to having a vaccination to protect against COVID-19 and its potential resultant health complications and risk of death, and these greatly outweigh the very low risk of pericarditis and myocarditis.

Health experts continue to recommend getting vaccinated against COVID-19 to protect yourself, your family and your loved ones.

What if I already have a cardiac condition?

People with a history of chronic cardiovascular conditions are at much greater risk of dying or suffering long-term health complications if they get COVID-19, so the advice is that they get vaccinated against COVID-19 as soon as possible. There is no current data to suggest that there is a higher risk for these people of developing myocarditis after receiving a COVID-19 vaccination than for the general population.

Chronic cardiovascular conditions include coronary artery disease, heart attack, heart failure, arrhythmias like atrial fibrillation, rheumatic heart disease, Kawasaki Disease, congenital heart disease, or people who have had a cardiac transplant or an implantable cardiac device.

In general, people with conditions such as acute rheumatic heart disease with evidence of active inflammation, and acute decompensated heart failure can still receive an mRNA vaccination. However, please consult with your doctor or other healthcare specialist for your specific case. People should not have a mRNA vaccine in the first six months after a confirmed case of myocarditis or pericarditis.

What are the symptoms to look out for?

The most common symptom of pericarditis is chest pain, usually worse on lying flat and on inspiration. Other signs and symptoms include:

  • Heart palpitations
  • Shortness of breath when lying down.

There are varying signs and symptoms for myocarditis due to its different causes, however common ones include:

  • Shortness of breath, whether at rest or during activity
  • Rapid or irregular heartbeat (arrhythmias)
  • Fluid build-up with swelling of the feet, ankles and legs.

It is important to speak to your doctor or seek medical help as soon as possible if you experience any of these symptoms.

How are pericarditis and myocarditis treated?

Early diagnosis and treatment of pericarditis and myocarditis usually reduces the risk of long-term complications, and a complete recovery is possible with treatment. This may include simply rest and medication, and treating any underlying chronic conditions. Anti-inflammatory drugs, like Nurofen, are often effective. Very occasionally, stronger medications and/or hospitalisation are necessary, but this is relatively rare.

In summary

The risk of a vaccine is far less than the health risk from COVID-19. These vaccines reduce the risk of serious COVID-19 by approximately 98 per cent. They are especially important in most adults with pre-existing cardiac conditions.

About the author

Professor David Celermajer

Professor David Celermajer has been with the Heart Research Institute since 1994, is Clinical Director of HRI and Group Leader of Clinical Research. He is an Academic Cardiologist at Royal Prince Alfred Hospital where he is Director of Adult Congenital Heart Services and Director of Echocardiography. He is also a Staff Cardiologist at the Children’s Hospital in Westmead. For his services as a researcher and clinician in the field of cardiovascular disease, he was appointed as an Officer of the Order of Australia. Read more about Professor Celermajer here.

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