As part of the enhanced monitoring system for vaccines against Covid-19, EPI-PHARE (ANSM-Cnam scientific interest group) conducted a new pharmacoepidemiology study on the risk of myocarditis after vaccination with a mRNA (Comirnaty or Spikevax).
An increased but low risk. There is indeed a risk of myocarditis after the first booster dose (third dose) but it is lower than after the second dose and decreases with the lengthening of the time between successive doses, according to a study by the National Agency for drug health, published July 22.
Higher cases in men under 30
Myocarditis is an inflammation of the myocardium, the muscle tissue of the heart. Viral infections, such as Covid, are a common cause of myocarditis, which can lead to hospitalization, heart failure or even sudden death. Myocarditis is also recognized as a very rare side effect of mRNA vaccines (Pfizer or Moderna) by the European Medicines Agency.
“The excess of cases of myocarditis associated with the third dose is globally estimated at 0.25 cases per 100,000 doses of the Comirnaty vaccine and 0.29 cases per 100,000 doses of the Spikevax vaccine, corresponding to 1 case of myocarditis attributable to the vaccination for the administration of 398,000 third doses of Comirnaty and 340,000 third doses of Spikevax”, further indicates the ANSM.
And to conclude: “The most significant excess cases were observed in men under 30 years of age, with a maximum of 1.2 cases per 100,000 third doses of Comirnaty, which corresponds to 1 case of myocarditis per 87,000 third doses”.
A previous study conducted by EPI-PHARE, the results of which were published in the journal Nature Communications, had shown that there was a risk of myocarditis in the week following vaccination against Covid-19 by mRNA vaccines, in particular after the second dose of the Spikevax vaccine in men and women aged 12 to 50 years.
This previous study had also confirmed the favorable clinical evolution of cases of myocarditis.
How to treat myocarditis?
In the event of myocarditis, hospitalization is necessary and lasts “at least 48 hours”, explains Dr. Manzo-Silberman to Doctissimo. “When we see that there is damage to the heart muscle, it is hospitalization in intensive care.” Myocarditis is a disease that we must especially monitor to detect possible complications. “You have to be sure that it is not an evolving infarction, that there is not an artery to unclog”, he adds to our colleagues.
According to the cardiology department of the CHUV, the treatment is mainly composed of anti-inflammatories and painkillers (for chest pain).