Covid is much more likely to cause heart problems among teenagers than from the vaccine., research has shown.
Millions of 12-to-15-year-olds have the option of taking up a second jab from tomorrow as efforts are increased prevent the spread of Omicron variant.
But 50 per cent of that age group in England have yet to sign-up for a first dose since the Covid jab was offered to them in late September.
Among 16-to-17-year-olds the figure is slightly better, so the reasons why youngsters are not signing up is not clear.
But vaccines have been linked to very rare cases of myocarditis, where muscles in the heart become inflamed causing chest pain, breathlessness, a pounding pulse and nausea.
The condition can develop after a viral infection such as flu and the heart is 'injured' by Covid or by the immune system’s reaction to it.
Men are more likely to be affected by myocarditis than women as the male hormone testosterone hampers cells in the body which can reduce inflammation.
Dr Mohiddin, consultant cardiologist at Barts Heart Centre in London said: "There’s a striking predisposition to myocarditis in younger men, which may be to do with their higher levels of hormones
"They usually develop heart problems about 10 days or so after viral infection, but in 90 per cent of cases it’s mild and they make a complete recovery."
Myocarditis has been linked to very rare cases in the Pfizer jab among teens and the Moderna jab as a booster in over-18s.
But there is no evidence that the Oxford- AstraZeneca vaccine triggers it.
Sir Chris Whitty announced plans in the autumn to vaccinate teenagers and said there was only a marginal benefit in health terms
They were offered the jab to keep schools open as much as possible and prevent disruption to pupils’ education.
Scientists from Edinburgh and Oxford universities last month found that for every million second doses of the Pfizer given to those aged 16 to 40 in the UK, there were three cases of myocarditis.
Health experts say Covid vaccine risks of myocarditis are small.
Dr Mohiddin told the Daily Mail : "My message to worried parents would be that the risks from teenagers not being vaccinated are greater than being vaccinated – even with milder Omicron in circulation."
The Medicines and Healthcare products Regulatory Agency, which monitors drug safety in the UK, there were 566 reports of myocarditis in all age groups following the Pfizer jab up to December 21m, but it led to four deaths
It adds: "The majority of fatal reports describe underlying illnesses in these patients that could provide an alternative explanation."
Under-18s should wait at least 12 weeks after having Covid infection to have a first or second vaccine government advice says.
But the risk of heart problems could be higher if a teenage boy catches the virus without knowing and shows no symptoms
Doctors say it’s impossible to say but any increase in risk would be small and myocarditis would be very mild.
