Cases of myocarditis associated with covid vaccines on the rise

Heart muscle involvement is mild, infrequent and occurs more in teenagers and young adults

2 min
A young man getting vaccinated against the coronavirus in Barcelona.

BarcelonaStatistically, there are few cases and most of them are mild. However, adverse effects associated with inflammation of the heart muscle, such as myocarditis or pericarditis, seem to have a tendency to increase as the covid vaccination campaign progresses, especially from the second dose onwards. The specific causes of this phenomenon are currently unknown, and the statistics do not indicate that it is a major public health problem, especially when compared with the millions of doses administered worldwide. However, an article published in the JAMA (Journal of the American Medical Association), the journal of the powerful U.S. medical association, notes that more cases of myocarditis and pericarditis are being detected than "expected" in young adults. The data "do not call into question" the benefits of mass vaccination, although they do provide "a point of concern," according to the study's authors.

According to the study, based on 1,626 cases of myocarditis reported by the United States Vaccine Adverse Events Reporting System (VAERS) seven days after vaccine administration, the figure exceeds what would be "expected" in teenagers and young adults, especially considering that the vaccine is administered to all age groups. According to the data, between the ages of 12 and 15 an incidence of 70.7 cases of inflammation in the heart muscle per million doses is achieved, and between 16 and 17 years it shoots up to 105.9 cases per million doses injected. When you jump to the next age range, 18 to 24 years, the rate returns to about 50 cases per million vaccinated and continues to decrease with increasing age

The head of the infectious diseases service at Hospital Parc Taulí in Sabadell, Manel Cervantes, sufficiently summarises the situation graphically: "There are quite a few cases; fortunately, the vast majority are mild". And he adds: "It is clear that they are cases linked to vaccines". However, heart muscle involvement rarely leads to failure and, in fact, subsides within a few days. "It is a benign process" in medical terms.

"Relevant, but rare"

The evaluation in JAMA focuses mainly on the effects of vaccines based on messenger RNA technology (Pfizer and Moderna) and reports a more marked increase in the casuistry after receiving the second dose. The work has been prepared by experts from the CDC (Centers for Infectious Disease Control), the FDA (U.S. Food and Drug Administration) and several American hospitals and university institutes.

These findings are "relevant", according to Hospital Clínic de Barcelona epidemiologist Antoni Trilla, since they "add new data on the safety and benefit of vaccination". Post-vaccination myocarditis against covid, he explains, is not a rare phenomenon, but it is "very infrequent". "The risk is, at present, lower than that of cardiac damage and other types of damage caused by the infection," he insists. Even so, he considers that vigilance must be reinforced in case this type of event experiences a sudden increase.

For Cervantes, the published data are "reassuring", since they partly correct previous studies in Israel which pointed to a more pronounced trend in this pathology associated with the covid vaccine. However, the expert believes that the results "invite reflection" on the need or not to vaccinate children under 12 years of age and on the need to repeat doses in young adults due to the "doubtful" benefit that vaccines may provide.