Vaccine-associated myocarditis mild compared to COVID-associated heart complications for children

Further evidence confirms that the benefits of COVID-19 vaccination in children and young adults outweigh the rare risks of myocarditis/pericarditis temporally associated with the mRNA vaccine.

An American Heart Association (AHA) Scientific Statement, published in Circulation, says most children and young adults experience mild COVID-19 disease and up to 20% were completely asymptomatic. Cardiovascular manifestations, including cardiogenic shock, myocarditis, pericarditis and arrhythmias in children are uncommon, it concludes.

Every 1 million doses of COVID-19 vaccine could prevent 11,000 COVID-19 cases, 560 hospitalisations and 6 deaths in males aged 12–29 years — a group the AHA says is at the highest risk for vaccine-associated myocarditis.

In return, 39–47 cases of vaccine-associated myocarditis might be expected.

Cases typically present at 2–6 days post-vaccination, can usually be managed with oral anti-inflammatory medications for relief of chest pain, and 86% resolve within a month.

Also published in Circulation was a multinational study which calculated the prevalence of definite/probable COVID-19-associated acute myocarditis among hospitalised patients at 2.4 per 1,000 and up to 4.1 per 1,000 including possible cases.

Most were males (61%) with a median age of 38 years. More than half the cases occurred in patients without COVID-19-associated pneumonia.

The study found the median hospital stay was 13 days including a median 6-day ICU stay for most patients (70%) which was frequently complicated by shock.

The estimated mortality at 120 days was 6.6% overall and 15.1% in those with pneumonia.

The results provide further confirmation that COVID-19-associated myocarditis is a more serious condition than COVID-19 vaccine-associated myocarditis.

MIS-C and longer term outcomes

The AHA Scientific Statement reviewed the presentation and management of COVID-19 and the rare complication of multisystem inflammatory syndrome in children (MIS-C).

“As many as 50% of children with MIS-C have myocardial involvement including decreased left ventricular function (defined as an ejection fraction <55%) in 28% to 55% of patients, coronary artery dilation or aneurysms in 12% to 21%, myocarditis in 17% to 18%, elevated troponin and BNP or NT-proBNP, or pericardial effusion in 23% of the patients,” it said.

“Structured follow-up of patients with MIS-C because of concern about progression of cardiac complications and an unclear long-term prognosis is suggested.”

The Statement said mid-term data after SARS-CoV-2 infection in youth were encouraging.

“Available data suggest that it is safe to allow asymptomatic youth and those with mild infection (upper respiratory infection symptoms and <4 days of fever) to return to sports after recovery from SARS-CoV-2 infection.”

“In contrast, until better outcome data are available, it is reasonable to consider screening youth with greater than mild SARS-CoV-2 infections or MIS-C with cardiovascular testing, including but not limited to cardiac enzyme levels, ECG, and echocardiogram, before return to sports.”

The AHA Statement said long-term COVID-19 outcomes were needed for children with and without acquired and congenital heart disease.

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