Heart inflammation after a Covid jab is not only rare but no more common than after other types of vaccinations, researchers have found.

As Covid vaccination programmes began around the world it emerged that some people – particularly young men – subsequently developed myocarditis, a type of inflammation of the heart muscle, or pericarditis, inflammation of the outer lining of the heart.

While cases were rare, the findings caused concern, with risk of such heart inflammation among the reasons cited by experts in the UK for the delay in expanding the vaccination programme to children.

Now research suggests that myopericarditis – an umbrella term that encompasses myocarditis and pericarditis – is not only uncommon after Covid jabs, but the risk of developing it is no greater than that posed by other types of inoculations, such as flu vaccinations.

“The overall risk of myopericarditis appears to be no different for this very new group of vaccines against Covid-19 than for traditional vaccines against other pathogens,” the authors write.

Writing in The Lancet Respiratory Medicine, researchers in Singapore describe how they carried out an analysis of 22 previously published studies, covering more than 405m vaccines doses around the world, that looked at the occurrence of myopericarditis after vaccination.

In total, 11 of the studies covered Covid jabs, although many did not consider those under the age of 12 years, while 11 looked at flu, smallpox, polio, and MMR (measles, mumps and rubella) vaccinations, among others.

The results reveal the incidence of myopericarditis is low after a Covid jab, with a mean incidence of about 18 cases per million doses. This is similar to incidence after a flu vaccine and after other types of vaccination.

When pooled together, non-Covid jabs had an average incidence of about 56 cases of myopericarditis per million doses.

The incidence is also far lower than incidence after the smallpox vaccine – although the authors note studies into the latter were conducted mainly among the US military, which is primarily composed of young men, potentially affecting the results.

Myopericarditis after Covid vaccination was relatively more common in the case of mRNA jabs, in younger people, after a second dose , and among men: incidence was 10-fold greater for men than women under 30. However, even among young men, rates of myopericarditis after a Covid jab were comparable to other vaccinations.

The authors add the risks of uncommon adverse events such as myopericarditis are outweighed by the benefits of vaccination, noting this includes a lower risk of infection, hospitalisation, severe disease and death from Covid itself.

But they suggest the study’s findings may help to tailor policy; for example, boys could be offered non-mRNA Covid jabs, although other issues may also influence such decisions, such as availability of such vaccines.

Dr Kollengode Ramanathan of the National University of Singapore, a co-author of the research, said: “These findings are important additions to the conversation when weighing the risk-benefits of Covid-19 vaccination and parents should be informed about the benefits and harms of Covid-19 vaccination, the local risk of exposure to Covid-19 infection at the time, and the risk of myopericarditis from Covid-19 infection itself at the time of vaccination of their adolescent children.”

Prof Beate Kampmann, the director of the Vaccine Centre at the London School of Hygiene & Tropical Medicine, who was not involved in the study, said it was important to take note of the findings but that the main message was myopericarditis after Covid jabs was very rare and no more common than after other vaccines. In addition, she said, the condition settled down with anti-inflammatory treatment.

“The risk of heart involvement and serious harm from Covid-19 itself is significantly higher than this rare side-effect, which primarily – and rarely – affects young males,” said Kampmann.

Prof Sir Nilesh Samani, the medical director at the British Heart Foundation, agreed.

“Millions of people around the world have had a Covid vaccine, virtually all without complication,” he said. “Getting Covid-19 can lead to severe illness including heart issues and people who are vaccinated have a much lower risk of getting other serious complications caused by Covid-19.”