The review of more than 8000 reported cases from 46 studies through researchers in Canada confirms previous reports that myocarditis is rare, but cases are higher in young men at one time after a momentary dose, and are likely higher after Moderna’s mRNA vaccine than after Pfizer. vaccine.
It also shows that even if cases are generally mild, the risk of myocarditis or pericarditis may decrease when the dose is currently given more than 30 days after the first dose.
However, the researchers caution that, overall, the evidence is of low certainty and say those findings want to be alongside the overall benefits of vaccination.
Myocarditis (inflammation of the central muscle) and pericarditis (inflammation of the fluid-filled sac surrounding the center) are rare but serious situations, caused by a viral infection. Reports of such situations following COVID-19 mRNA vaccination have fueled ongoing surveillance and research. .
The effects show that rates of myocarditis after mRNA vaccines were in adolescents and young adult males (50 to 139 cases consistent with one million in people aged 12 to 17 years and 28 to 147 cases consistent with one million in people aged 18 to 29 years).
For women and children older than 5 to 11 years and women older than 18 to 29 years, rates of myocarditis after vaccination with Pfizer can be less than 20 cases per million.
For other people aged 18 to 29 years, myocarditis is greater after vaccination with Moderna than with Pfizer, and for people aged 12 to 39 years, myocarditis or pericarditis may decrease when the current dose is given more than 30 days after vaccination. of the first dose.
The express information to men over 18 to 29 years old implies that the dosing period could increase to more than 56 days to especially reduce the rates of those conditions.
As such, researchers say giving Pfizer instead of Moderna and lengthening dosing periods may be favorable for young people.
But they note that the clinical course of myocarditis in children aged five to 11 years, after a third dose, and for those who have already had myocarditis after mRNA vaccination is largely unknown. And while the short-term evolution has been fairly mild and self-limiting, they say more knowledge is needed for a longer-term diagnosis.
They also acknowledge some limitations of their review, adding the evolving literature on COVID-19 and the threat of misdiagnosis. However, their strategy of comprehensive, peer-reviewed studies and use of a diversity of data resources allowed them to capture the most recent data. .
As such, they conclude: “As the COVID-19 pandemic enters its third year, continuous monitoring of myocarditis is needed after mRNA vaccines, especially in young people, after the third dose (and next doses) and in previous cases, to make ongoing decisions. “-doing for COVID-19 Boosters”.
And they call for greater follow-up of other people with applicable underlying conditions, long-term follow-up of patients with myocarditis, and other studies to “improve the mechanisms of myocarditis and pericarditis after vaccination. “
This large number of peer-reviewed studies continues that COVID-19 mRNA vaccines are relevant with a rare but increased threat of acute myocarditis and pericarditis, U. S. researchers say in a similar editorial.
They note that key uncertainties remain, adding the dangers related to boosters, the dangers related to the number one vaccination of young children, and the long-term outcomes of those with myocarditis.
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