The mRNA vaccines against covid, those from Pfizer/BioNTech and Moderna, slightly increase the risk of myocarditis. It was already verified when injections began to be given, especially among young men, although, after analyzing the cases -which had not been seen in the trials-, the regulatory agencies concluded that the benefit of the vaccine continued to outweigh the risk of suffering this unusual inflammation of the heart muscle, because it can also be caused by infection to a greater extent.
As published by the US Center for Disease Control (CDC), if it is estimated that there are about 9 cases of myocarditis per 100,000 people per year in the US, due to covid infection they rose to 150 cases per 100,000. Among children under 18 years of age, the incidence of the pathology was estimated between 2007 and 2016 in less than one case per 100,000 minors. The European Medicines Agency (EMA) described a few months ago the effect of myocarditis and pericarditis due to vaccination as “very rare”, less than 10 cases per 100,000 people or 100 per million.
Now, a CDC study further quantifies the risk of myocarditis from mRNA vaccines. The researchers, in the work published on Tuesday by the journal JAMA, analyzed the 1,626 cases of myocarditis reported to the US system for reporting adverse effects from December 2020 (when vaccination against covid began) until the end of August last year.
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It meant more than 192 million vaccinated people over 12 years of age (in that period the Pfizer vaccine was given to people over 12 and the Moderna vaccine to people over 18). Adverse effects occurred within seven days after vaccination (especially the first three days). The researchers concluded that cases of myocarditis exceeded the usual rates for this heart condition in various age groups.
In their study, the researchers observed that 73% of cases (1,195) occurred in those under 30 years of age, 82% in men, and also 82% occurred after the second dose. The highest rate of cases was seen among adolescents (a third of cases, 543). There were 105.9 cases of myocarditis per million doses of the Pfizer vaccine among 16- to 17-year-olds and 70.7 cases among 12- to 15-year-olds. Among men ages 18 to 24, there were about 52.4 cases per million Pfizer vaccines and 56.3 in Moderna’s.
Suffering from covid can increase a citizen’s risk of suffering myocarditis by 16 times, the authors of the study recall, for this reason they maintain that the risk derived from vaccination must be contextualized with the benefit of getting these injections.
There were 106 cases of myocarditis for every million doses of the Pfizer vaccine in 16- and 17-year-olds
96% of those affected had to be hospitalized and were treated, above all, with non-steroidal anti-inflammatory drugs, the common treatment for the pathology. Most of those affected suffered symptoms for a couple of days. In 87% of those admitted, the symptoms (chest pain, shortness of breath) had disappeared when they were discharged. Only two had to be intubated.
Along with myocarditis, inflammation of the heart muscle, cases of pericarditis were looked at, in which the layer that covers the heart is inflamed.
Cases after vaccination heal faster than usual
Myocarditis already usually affects children and young people and men, as a reaction of the immune system to a viral infection. Sometimes it does not require treatment and others, in the study it is recalled that, in general, in 6% of cases, it can lead to serious heart failure and even require a transplant or be fatal.
Until now, such a clear relationship between pathology and vaccination had never been seen, but myocarditis had already been associated with the measles vaccine, after giving this injection to the US military.
The study indicates that myocarditis associated with the covid mRNA vaccine manifests itself much faster and also heals faster than usual in this pathology. One hypothesis that has been raised is that the vaccine would not be the cause but the trigger of the pathology in people who are already susceptible.
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The unprecedented vaccination of so many millions of people against covid in a short time has provided more information. In more detail, the more than 192 million vaccinated in the period studied, received 354 million doses and 1,991 suspected cases of myocarditis and 684 of pericarditis were reported among those who had received at least one dose (2,132 cases of myocarditis reported until this January ). Only 1,626 of the cases through August were considered by the CDC to be truly myocarditis or pericarditis (the patients had EKGs, MRIs and lab tests done).
The CDC studies two deaths of people under 30 years of age that could be related to myocarditis, but states that this pathology has not been seen in any other death of young people who had been vaccinated.
Women: fewer cases, but especially among those vaccinated with two doses of 16 and 17 years
The rates are considered higher than usual (the researchers compared them with those of the years 2017-2019 in different ages and both sexes) for those vaccinated with one dose of Pfizer between 12 and 24 years and those vaccinated with two doses between 12 and 49 years, as well as for those vaccinated with one and two doses of Moderna between 18 and 49 years.
Among women, the rate of cases is lower, but also higher than usual among those vaccinated with two doses of Pfizer between the ages of 12 and 30 and with Moderna between the ages of 18 and 39. There were 11 cases per million vaccines among those of 16 and 17 years old; 8.2 cases among those between 25 and 29 years old; 6.8 between 18 and 24 years old and 6.3 between 12 and 15 years old.
Warning about level sport after myocarditis
The researchers therefore confirm that myocarditis is “a rare but serious” adverse effect of vaccines, which the drug agencies have already stated in the prospectuses. Those who suffer from it can get another dose of the vaccine, but in medically controlled cases.
The CDC will follow cases of myocarditis longer term. The study already recalls that the American Association of Cardiology recommends (before the covid vaccine) to those who have suffered the infection to avoid competitive sport in the following 3-6 months and not to practice it again without first passing tests. such as electrocardiograms in which no alterations are observed.
The study has not analyzed the possible risk among children under 12 years of age, although in childhood vaccination the cases that were seen months ago as soon as the vaccination of adolescents and young adults began have not been detected.
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