What we know about myocarditis and the Covid-19 vaccines

The rollout of Covid-19 vaccinations for children aged 12 to 15 is due to begin in schools next week after being approved by the UK’s four chief medical officers.

The decision-making process has been “long and, at times, seemingly painful”, said the BBC’s health correspondent Nick Triggle, because it is a “finely balanced call”.

Healthy children are at a low risk from Covid, meaning the benefit of vaccination is only marginal, with efforts to avoid school disruption just tipping the balance in favour of jabs.

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However, “some concern has been raised about rare side-effects from the Pfizer/BioNTech and Moderna vaccines, in particular a condition called myocarditis”, said The Guardian’s science editor Ian Sample.

What is myocarditis?

According to the British Heart Foundation website, myocarditis “is inflammation of the myocardium - the heart muscle”. This inflammation is usually caused by a viral, bacterial or fungal infection; a chest infection; or an auto immune disease,

Symptoms

Common symptoms include a stabbing pain or tightness in the chest, shortness of breath, flu-like symptoms and abnormal heart rhythm.

Potential complications

“Most people with myocarditis recover completely, either with or without treatment, and have no lasting symptoms or complications,” said heart muscle charity Cardiomyopathy. Some people do not experience symptoms at all, but others may suffer complications.

Severe myocarditis can cause permanent damage to the heart, which can increase the risk of stroke or heart failure.

Link to Covid vaccines

Earlier this month, government advisers on the Joint Committee on Vaccination and Immunisation (JCVI) announced that a review of data from the UK, US and Canada had found “increasingly robust evidence of an association between vaccination with mRNA Covid-19 vaccines and myocarditis”.

But myocarditis was a “very rare adverse event”, they added, and was more common following a second dose of an mRNA vaccine - which include the Pfizer and Moderna jabs - than after the first dose. The risk of developing heart inflammation was found to be around three to 17 per million healthy 12- to 15-year-olds after a first dose, and 12 to 34 per million after the second jab.

Cases of myocarditis following vaccination were usually resolved “within a short time”, but insufficient evidence was available to be certain about any possible longer-term damage, the JCVI said.

Two recent US studies, by a team from Ohio and by researchers from four other US states, appear to disagree about whether being infected with Covid or being vaccinated against the virus is more likely to cause myocarditis. Neither study has been peer reviewed.

The JCVI concluded that children aged 12 to 15 with underlying health conditions should continue to be vaccinated against Covid, but “stopped short” of recommending universal vaccination for the age range, reported Pulse magazine.

“Overall, the committee is of the opinion that the benefits from vaccination are marginally greater than the potential known harms but acknowledges that there is considerable uncertainty regarding the magnitude of the potential harms,” the government advisers said.

But they stressed that this opinion was based only on a health perspective, adding: “The government may wish to seek further views on the wider societal and educational impacts from the chief medical officers of the four nations.”

The four medical chiefs subsequently decided that such benefits outweight the risks, noting that education is crucial for mental health and well-being, particularly in deprived areas.

As parents and children weigh up whether to consent to the jabs, which are not mandatory, other experts have been giving their views on the myocarditis link.

Dr Liz Whittaker, infectious disease lead at the Royal College of Pediatrics, told Radio 4’s Today programme on Tuesday that although around 600 young people in the US had been admitted to intensive care with myocarditis-related chest pain, the admissions were a precautionary measure and most required only simple treatment such as ibuprofen.

Swelling was seen “all the time” with other viruses in children, she said, and there was “optimism” that it would not cause lasting damage.