The son of a friend of mine, a student aged 20, developed myocarditis after his first Covid jab. Should he have his second, his mum asked me.

Myocarditis is inflammation of the heart muscle, and any mention of a heart problem will scare parents to death, but it’s not as bad as it may seem. Just how dangerous this side effect is still isn’t clear and, according to some experts, it might not be a cause for concern at all.

However, the US Food and Drug Administration has paused its approval of Moderna’s vaccine for adolescents – as it is reviewing data from Europe on the risk of myocarditis following mRNA vaccination used to combat Covid.

My friend’s son is unlucky. US data shows it’s a very rare condition, occurring in only about 70 out of a million vaccinations.

But according to the EU, Moderna’s shot is more likely to cause this ­inflammation in adolescents. Several Scandinavian countries no longer give Moderna to people under 30.

But there’s good reason for ­optimism. US data from millions of vaccinations show the inflammation, when it occurs, goes away within a matter of days without any serious consequences. Sarah Long, a ­paediatric infectious disease expert at Drexel University College of Medicine, Pennsylvania, US, and a member of the vaccine advisory panel of the Centers for Disease Control and Prevention, thinks that the post-vaccine heart inflammation might be different from myocarditis from other causes. In fact, it’s so different, and less severe than typical myocarditis, she says, that giving it the same name has created unnecessary worry over the condition.

“Let’s not call this myocarditis,” Long says. “Give me a patient with vaccine-associated myopericarditis every day over one who has true viral myocarditis.”

Long says the inflammation from the vaccine is different from other heart inflammations as it isn’t concentrated in the heart muscle itself, it’s in the lining around it – the pericardium.

Moreover, the lining isn’t essential for a healthy heart. Long also points out that surgeons sometimes remove it ­altogether during heart ops and patients come to no harm – and the CDC hasn’t recorded a single death from the condition.

“In vaccine-related inflammation, everyone was up and running in five days,” says CDC scientist Matthew Oster.

Children experiencing chest pain is certainly nothing to be brushed off lightly, says Long.

“Nobody has died of myopericarditis, and children are dying of coronavirus,” she says. “So, of course, it’s a risk-benefit ratio that comes out in the direction of vaccination.” Wise words.