Myocarditis after vaccination remains very rare

/ Sebastian Kulitzky, Stockadopicom

OXFORD – Myocarditis is a rare complication of COVID-19 vaccination. This has changed according to an updated analysis in Rotation (2022; DOI: 10.1161 / CIRCULATIONAHA.122.059970) did not change even after boosting.

The risk of SARS-CoV-2-induced myocarditis was lower in most groups. Most often, the vaccination reaction is observed in men younger than 40 years after the second dose of mRNA-1273.

Myocarditis is a very rare disease. The trigger is usually a viral infection. Inflammation in the heart muscle can impair pump function or lead to an irregular heartbeat. This can put the health and life of patients at risk. However, most recover after a short time with or without treatment.

At the beginning of the vaccination campaign, reports of myocarditis, which occurred mainly in young people after vaccination, caused an uproar. However, it soon became apparent that complications are very rare.

A team led by Julia Hebsley Cox already conducted a study in December nature medicine showed that complications are rarer in most age groups than with SARS-CoV-2 infection, which, like other viruses, can also trigger an inflammatory reaction in the myocardium.

At that time, only data up to August 2021 was taken into account. Now the team has extended its analysis until mid-December 2021. At this point, the first people have been boosted.

The analysis was again performed as an ‘autonomous case series’, in which different time periods of the same people are compared to each other. This avoids sources of error that can arise in case-control studies when comparing different groups of people.

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Showing how rare complications are, of the 42.8 million English people vaccinated against COVID-19 between 1 December 2020 and 15 December 2021, only 2,861, or 0.007%, were hospitalized with myocarditis. Of these, 617 cases (0.001%) occurred within the first 28 days after vaccination, and thus could be a complication of vaccination.

In fact, the risk of developing myocarditis after infection with SARS-CoV-2 was higher than after vaccination – even though the purpose of vaccination is not to protect against myocarditis associated with SARS-CoV-2. It’s about preventing the most common and dangerous consequences of COVID-19.

According to a Hippisley-Cox analysis, 35 patients per million people develop myocarditis after testing positive for SARS-CoV-2 but before vaccination. On the other hand, in the first 28 days after the first dose of BNT162b2 and mRNA-1273, two additional myocarditis events are expected for every million vaccinated people. After the second dose of BNT162b2 and mRNA-1273, there were 2 and 34 additional myocarditis events per million.

The second dose of mRNA-1273 is incompatible with the additional 34 events per million people. This is especially true for men under the age of 40, for whom Hepsley Cox estimates an additional 97 events per million.

By the way, the increase in myocarditis in women after the second vaccination with mRNA-1273 was significantly less. Hippisley-Cox found 7 additional cases of myocarditis per million vaccinations with mRNA-1273. This is no more than in unvaccinated women, of whom 8 additional cases of myocarditis per million people would be expected after infection with SARS-CoV-2.

The researcher was only able to provide a few numbers for the booster dose. So far, they do not indicate a renewed increase in myocarditis. The number of additional diseases in men (all age groups) was 3 myocarditis per million.

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This may be due to declining media attention. In their analysis, Hippisley-Cox cannot rule out that public interest led clinicians to pay more attention to myocarditis symptoms after vaccination with mRNA-1.273 and then, out of caution, referred patients to hospital earlier.

Restricting them to deaths may have avoided this error. However, these were generally rare. According to the publication, 345 people died of myocarditis within 28 days of hospitalization in England. © rme / aerzteblatt.de

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