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Explainer: What's The Deal With COVID-19 Vaccines And Myocarditis?


Dr. Katie Spalding

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer


tl;dr no. Image: Romariolen/Shutterstock

If you’ve been paying attention to social media recently, you may have noticed the development of a new and pretty heated topic: vaccine-induced myocarditis.

And, like a lot of news from the past couple of years, it’s because of COVID-19 misinformation.


Let’s take a look at what’s really going on – what myocarditis is, whether there’s a link to vaccines, and most importantly, whether we should be worried.

What is myocarditis?

Myocarditis is an inflammation (that’s the -itis) of the heart muscle (the myocardium). It’s actually part of the body’s innate immune response – in Europe and North America, it most often occurs as a reaction to a viral infection like the flu or hepatitis.

It can be caused by other things too though, and many cases worldwide are a result of infection with Chagas disease – which is parasitic. Then there are bacterial infections, toxins, autoimmune disorders, and even certain medications.


Is myocarditis dangerous?

Well, it’s certainly not good – it can cause all kinds of nasty symptoms like shortness of breath, stabbing pains and tightness in the chest, difficulty breathing when resting, and flu-like symptoms such as tiredness and fever. In extremely rare cases, it can even cause sudden death.

In some cases, it can interfere with your heart’s electrical system, making your heart beat in an irregular rhythm – and if left untreated, it can seriously impact the strength of your heart muscle. That’s why if you experience any symptoms of myocarditis, you should seek medical attention immediately.

The good news is, more than four cases out of five go away without treatment – and many of those who do need medical care will only need a course of anti-inflammatory drugs or antibiotics.


Sometimes more intensive solutions are needed, up to and including extracorporeal membrane oxygenation (ECMO) or even a heart transplant.

Why is it in the news?

Vaccine-induced myocarditis has been a hot-button topic since – well, pretty much since the vaccine rollout began. It didn’t take long for case studies to surface conclusively linking mRNA vaccines – Moderna and Pfizer – with a slightly increased risk of myocarditis, especially in adolescent males.

But while health organizations such as the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) swiftly issued statements explaining the overall health benefit of vaccination and relatively low incidence of myocarditis, various misinformation merchants jumped at the memeing potential of the findings.


Now, experts are having to tackle mainstream tabloids and hugely influential broadcasters who are convincing their audiences that getting a COVID-19 vaccine will cause myocarditis.

Does the vaccine cause myocarditis?

It’s certainly true that cases of myocarditis following vaccination, particularly with an mRNA vaccine, have been reported in countries around the world. That’s likely due to the way the vaccines work – remember, vaccines don’t fight disease themselves, they teach your body how to fight it. They do that, in most cases, by pretending to be that disease.

“COVID itself presents to your body a protein it’s never seen before, which is the spike protein,” explained Dr Raj Puranik, clinical practice advisor with the Cardiac Society of Australia and New Zealand.


“When people say [myocarditis is] vaccine-related, what happening is that the mRNA vaccine […] turns on your own body’s machinery to produce this protein that is foreign to your body, and then your body responds to it.”

Estimates on the actual increase in risk range from around three to over 23 times higher, depending on which research methods are used. One thing is important: the overall risk remains very low.

“Thirty times a small number is still a small number,” cardiologist Dr James de Lemos told the New York Times. “The math still favors vaccination in adolescents and children.”

So should we worry about myocarditis from the COVID vaccine?


Those numbers may seem scary, but there are some important caveats to bear in mind. First of all, those figures are a comparison with a healthy population – but of course, we’re not taking vaccines because we’re healthy, we’re taking them to stop us from getting unhealthy.

“If you look at an isolated risk, you could really get yourself very worked up and scared,” Dr. Brian Feingold, an expert on heart inflammation in children at UPMC Children’s Hospital of Pittsburgh, told the NYT.

However, he added, permanent heart damage is “way more likely” from a COVID-19 infection.

The better comparison, then, is to compare the incidence rates of myocarditis following vaccination to the rates following a COVID-19 infection – and that’s where the picture starts to look clearer.


Remember, myocarditis is most often caused by a virus, and SARS-CoV-2 is no exception: virtually every study that has been carried out on the subject agrees that catching COVID is much more likely to cause inflammation than getting vaccinated.

Dr Grace Lee, Professor of Pediatrics at Stanford University School of Medicine and Associate Chief Medical Officer for Practice Innovation at Stanford, agrees. Writing in the New England Journal of Medicine, she pointed out that “[in] the population-based cohort in the study conducted by Barda and colleagues, the risk ratios for myocarditis were 3.24 […] after vaccination and 18.28 […] after SARS-CoV-2 infection.”

That makes myocarditis after COVID-19 nearly six times more likely than after vaccination – or, to put it another way, if you’re scared of myocarditis, you should be more worried about COVID-19 than the vaccine against it.

Another thing to bear in mind is that, so far, vaccine-induced myocarditis mostly seems to be short-term and mild – “unsettling, but rarely life-threatening,” de Lemos said to the NYT.


However, that isn’t necessarily the case after a COVID-19 infection – and if you want one takeaway about the link between vaccines and myocarditis, it should probably be this, explained by Dr Puranik:

"The really important issue here is that if you developed myocarditis after a vaccine – were you to have seen this protein from COVID itself, it could have killed you.”

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.


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