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A large French study analyzed the occurrence and impact of myocarditis occurring after an anti-Covid vaccination. These results are generally reassuring with very few complications following their onset, with a year and a half of hindsight.
In France, a pharmacoepidemiology study conducted by Epi-Phare, in collaboration with the ANSM and the CNAM, provides reassuring information on the evolution of myocarditis associated with mRNA vaccination against Covid-19. Published in the Journal of the American Medical Association (JAMA) on August 22, 2024, this study followed 558 patients to assess the 18-month prognosis of these rare but worrying cardiac inflammations.
Less serious than myocarditis linked to Covid-19
Between December 27, 2020 and June 30, 2022, 4,635 confirmed cases of myocarditis were identified in people aged 12 to 49 years hospitalized in France. Of these cases, 558 occurred after administration of an mRNA vaccine, 298 occurred following infection with SARS-CoV-2, and 3,779 myocarditis cases were related to other causes.
The results are clear: post-vaccination myocarditis, although serious, is significantly less severe than that caused by direct Covid-19 infection. Patients with myocarditis after mRNA Covid-19 vaccination had fewer cardiovascular complications (5.7%) at 18 months than patients with myocarditis attributable to Covid-19 or other causes (12.1% and 13.2%, respectively).
Reassuring results
Follow-up revealed that of the 558 cases studied, the majority of patients were young men, often under 30 years old, confirming the demographic profile at risk.
These results do not in any way call into question the value of vaccinating young adults in 2021, according to epidemiologist Mahmoud Zureik, director of Epi-Phare. In The Parisianhe recalls: “From 2020 to the end of August 2021, there were more than 75,000 hospitalizations and around 700 deaths linked to Covid among those under 50. If we take these data into account in the face of the 558 cases of myocarditis, including only one death, we did well to vaccinate young people.“.
A benefit/risk balance to be reassessed
The Epi-Phare study is part of a series of research aimed at understanding and alleviating fears related to vaccination. With persistent uncertainty in public opinion about the side effects of mRNA vaccines, these new data help to strengthen confidence in vaccination by showing that, despite the occurrence of myocarditis, the long-term effects are generally favorable and most reversible.
However, it is still recommended to continue to closely monitor these rare cases and to regularly reassess the benefit/risk balance, particularly in young people, at a time when new mRNA vaccines are being considered against influenza, shingles, certain cancers, etc.
“Even if the risk is very low, it should not be given to people who otherwise have almost no risk of severe forms of COVID. As always in medicine, the benefit-risk balance must be weighed accordingly. Moreover, the High Authority of Health now recommends vaccination for the elderly and the most fragile” insists Dr. Gérald KIERZEK, emergency physician and medical director of Doctissimo.”Studies have even shown the absence of benefits of COVID vaccination in people under 65 without comorbidities” he adds.