Cases of myocarditis following mRNA Covid-19 vaccination, especially in young people, have caused concern at times in recent years.
But these illnesses were generally milder than cases of myocarditis resulting from Covid-19 disease or other causes. French scientists have now proven this.
Laura Semenzato and her co-authors from the French Medicines Agency (ANSM) have published their study in the Journal of the American Medical Association (JAMA; DOI: 10.1001/jama.2024.16380). They were interested in investigating the long-term complications of people with myocarditis (observation period: one and a half years) between the end of December 2020 and the end of June 2022. For this purpose, they had access to the data of all those affected in France.
Study from France
The scientists: “A total of 4,635 people were hospitalized with myocarditis. 558 were after vaccination, 298 after Covid-19 disease and 3,779 patients because of ‘conventional’ myocarditis.” The most common cases of myocarditis were after Covid-19 vaccination with an mRNA vaccine after the second dose. 85 percent of those affected were men.
The risk of further complications within 18 months was very unevenly distributed and suggests a significantly lower risk after a Covid-19 vaccination than after a real illness caused by SARS-CoV-2 or other causes of myocarditis. For example, 5.7 percent of people had to be readmitted to hospital due to cardiovascular problems after myocarditis, probably related to a vaccination. However, after Covid-19 myocarditis (illness), the figure was 12.1 percent within a year and a half, which is significantly more. This risk was even slightly higher – 13.2 percent – for patients after “conventional” myocarditis. Myocarditis can have a variety of causes.
The two vaccines showed a lower risk of myocarditis after vaccination with the Moderna mRNA vaccine (mRNA-1273) compared to the BioNTech/Pfizer vaccine (BNT162b2). However, the difference was not statistically significant. One patient from the mRNA myocarditis group died within 18 months. This meant a mortality rate of 0.2 percent. In contrast, four people from the group with myocarditis after Covid-19 disease died (1.3 percent) and 49 patients after “conventional” myocarditis (also 1.3 percent).
