Moderna's anti-Covid vaccine poses a small risk of heart problems, but without serious consequences, shows a study published Thursday, December 16 and carried out on the entire Danish population.
This study, published in the
British Medical Journal
(BMJ), also reports heart risks associated with the Pfizer vaccine, but only in women.
"Vaccination with (Moderna) is associated with a higher risk of myocarditis or pericarditis in Danes, primarily 12-39 year olds"
, summarize the authors.
Read also Pfizer vaccine protects 70% of severe cases of Omicron, according to a South African study
Myocarditis and pericarditis are inflammations of the heart.
The first affects the myocardium, the main heart muscle, and the second the pericardium, the membrane that surrounds the heart.
These conclusions are in line with previous studies which have prompted several health authorities, including those in France and Denmark, to suspend the use of the Moderna vaccine for the youngest.
Iceland has even ended it for all adults.
This work is the first carried out at the scale of the population of an entire country, Denmark being at the forefront of the collection and use of public health data.
According to this study, the risks of myocarditis / pericarditis appear three to four times higher in Moderna vaccinees, in the month following vaccination, than in Pfizer / BioNTech vaccinees. As for the latter,
"it is not associated with a higher risk of myocarditis or pericarditis than in women,"
note the researchers, admitting to being surprised by this conclusion. They insist in any case on the fact that these heart problems remain rare, including in those under 40 vaccinated by Moderna, since only about 0.005% of them are concerned. Importantly, these problems were mostly mild and no death or cardiac arrest was observed in vaccinees with myocarditis or pericarditis.
Read alsoWhy are vaccines less effective against the Omicron variant?
More broadly, the fact of having received one of these two vaccines is even associated with a lower risk of death from cardiac arrest compared to unvaccinated, even if this is not the main endpoint evaluated by the 'study.