Clinical guidance on detecting and managing rare cases of heart inflammation in children after Covid-19 vaccination has been issued by the UK Health Security Agency and RCGP.
It follows 432 reports of myocarditis and 332 reports of pericarditis following the use of the Pfizer vaccine and 101 reports of myocarditis and 57 reports of pericarditis in patients who had the Moderna vaccine.
In the under 18s, the reported rate for heart inflammation (myocarditis and pericarditis) is 10 per million doses of the Pfizer vaccine, the UKHSA said.
Most cases are mild or stable and patients recover without treatment, the advice says but those who are acutely unwell or unstable should be referred to hospital immediately.
It notes that a significant left ventricular fibrosis has been described in a high percentage of children admitted to hospital with myocarditis, with a small percentage of these having non-sustained ventricular tachycardia.
As yet there is no follow up on hospitalised patients and long-term consequences are not known.
The guidance recommends that children who have symptoms within 10 days of the vaccination do not need referral to secondary care unless acutely unwell or unstable but they should be seen face to face and vital signs taken.
Hospital referral is needed in the case of significant chest pain, tachycardia or tachypnoea, new and unexplained dyspnoea, palpitations or dizziness or general clinical concern and should involve paediatric cardiology teams.
In young people under 40 who had a vaccine within the past 10 says, similar guidance applies but clinical judgement should be used to determine if the diagnosis is one of concern and needs referral to secondary care for ECG, inflammatory blood markers and troponin, the recommendations advise.
Patients with mild symptoms who do not require further tests or in who initial tests were normal should be told to go back to the GP if symptoms persist or worsen in the next five days.
Covid vaccination should be delayed for 12 weeks following a positive Covid test results in children aged 12-17, according to recently updated guidance.
The updated advice was based on emerging evidence from the UK and other countries that leaving a longer gap may further reduce the already small risk of myocarditis.