Is myocarditis a risk of COVID jabs in kids?

One of the reasons that the JCVI, the group responsible for advising on UK vaccine policy, struggled to provide a clear recommendation on the vaccines for children, and hence referred the question to the chief medical officers, is because the vaccines carry a small risk of a side effect called myocarditis. The rate at which this occurs is not much higher than the rate we expect to see in the general population anyway, and it occurs more often in unvaccinated people who develop coronavirus infection compared with those protected by a vaccine. So what is myocarditis, and is it a major threat for young people, or are we worrying too much? Trisha Singh is a cardiology researcher looking at myocarditis at Edinburgh Royal Infirmary and spoke with Chris Smith...

Trisha - So myocarditis is inflammation of the heart muscle. Usually when we see patients in hospital, they usually present with, most commonly, chest pain, breathlessness, palpitations. However, some people may not get very many symptoms at all.

Chris - And when people have this, does it get better? Does it get worse? Does it stay the same?

Trisha - In most people, myocarditis does get better and your heart muscle recovers, and the inflammation settles down. A very small percentage can go on to having further problems down the line, but that is a very, very small percent.

Chris - Do we know what causes it?

Trisha - The most common cause of myocarditis is usually following a viral infection. Now this can be a flu-like virus, it can be a tummy bug, skin infections. Less common causes of myocarditis can include medications. It has been noticed in vaccines, not just the COVID-19 vaccine but also in the past, we've seen it in smallpox and also influenza vaccines.

Chris - And can people who catch the new coronavirus, get it. Is it one of the consequences of coronavirus infection?

Trisha - It is. So we have seen patients who unfortunately have developed a COVID-19 infection have also had cases where they've also developed myocarditis as well

Chris - But do we know what's actually going on? If you were to look at the heart, when an individual is suffering with a case of myocarditis, what is actually happening that's making those symptoms and making the heart behave in that way?

Trisha - That very much depends on the cause of myocarditis. If it's, for example, viral infection related, what's happening is that all of your inflammatory cells that your body normally releases when it's fighting an infection infiltrate the heart muscle, and cause inflammation in the muscle itself. And that inflammation of the heart muscle is what causes the symptoms.

Chris - And so we think that there are some people who, when they get vaccinated, the immune response they make to the vaccine does the same thing as though they were infected with the virus for real, and that inflammatory response spills over temporarily into the heart?

Trisha - I think the difficulty with vaccine related myocarditis is we're not entirely sure the process in which it causes myocarditis, and there's lots of theories. So one of them is that, you know, your immune system kind of goes into hyperdrive and as a result can result in myocarditis

Chris - It's happening to more boys than girls. Do you think that that's a real thing? Or do you think that that actually is a statistical artefact, it's just that we happen to have detected more cases in males than females so far?

Trisha - No, I think that's actually a genuine thing. So myocarditis in general, even when it's not vaccine related, is far more common in young people. And when I say young, kind of, under the age of 30, and far more common in men

Chris - What then are the implications for vaccination in the context of the new coronavirus in young people? Do you think that it's happening enough that we should worry? Or do you think that it's broadly self-limiting, not really a problem, and therefore it shouldn't receive the kind of prominence it has? Are we blowing this out of proportion?

Trisha - The majority of myocarditis is self-limiting and people have a very good prognosis down the line. I wouldn't say that we're blowing it out of proportion, but what I would say is, you know, the number of cases that we're seeing which are vaccine related is A, very, very small and B, I think it's a balance of risk and benefit that you get from the vaccines. And I think the benefit that we're getting from vaccines is much higher currently compared to the number of cases that we're seeing which are vaccine related.

Chris - What we have seen is that the Chief Medical Officer said that we're going to give children one dose. Some people are interpreting that as because the cases of myocarditis have been more common after the second dose. Is it that they're just saying one dose because we're going to see what happens after one dose, we might not need to give anyone any more boosters, or are they actually acting on the fact that there does appear to be this slight increase in numbers after the second dose, and that's why they've taken that as a cautionary step?

Trisha - Probably a combination of both. And I think we've seen less myocarditis in general than we normally do in the last year, and I suspect a lot of that is because of the effects of lockdown. You know, we haven't seen as many people with flu symptoms and similarly, we haven't seen many people with myocarditis. And I think with giving the single vaccine in children, at least for the time being, it's probably a combination of both.

Chris - That's fascinating that you're saying we've actually got less myocarditis at the moment than we would expect to seasonally anyway! Could at least a proportion of the association with apparently the vaccine myocarditis be in fact that kids are now coming out of lockdown and they're catching the other stuff again, that might be causing myocarditis is not the vaccine at all?

Trisha - Yes, absolutely. And I think that's why it's really important, you know, when you are seeing children or adults, anyone in hospital, and they've got myocarditis, there's a good chance that they could just be having this because, you know, they picked up a viral infection somewhere else. And the myocarditis is related to that rather than purely vaccine related.