Science

Heart Complications More Likely From Covid Than From Vaccines, Study Finds

Topline

Covid vaccines that use mRNA technology carry a slight risk of heart complications for some individuals, but far less than the risk of heart complications that comes with having a Covid infection, according to a study published Friday by the Centers for Disease Control and Prevention.

Key Facts

The study tracked incidences of myocarditis, a typically mild inflammation of the heart muscle that tends to affect males, and pericarditis, a typically mild inflammation of the sac containing the heart, following Covid infection and following doses of Pfizer-BioNTech and Moderna’s mRNA vaccines.

The risk of heart complications after vaccination was highest among males age 12-17, especially following a second dose, when there was a roughly .04% (1 in 2,786) risk of developing myocarditis or pericarditis within 21 days—still 1.8 times lower than the roughly .07% (or 1 in 1,541) risk of developing those disorders following Covid infection for males in that age range.

Women were at lower risk than men of developing heart complications following vaccination, with women age 18-29—the highest-risk female group—reporting at most a .01% (or 1 in 17,241) risk of myocarditis or pericarditis within 21 days of vaccination.

These findings reinforced previous CDC research indicating that mRNA vaccines very rarely cause heart complications, and that male adolescents and young adults are at greatest risk, especially following their second shot.

Heart complications were so rare among some patient groups that it was difficult to precisely estimate how much lower the risk was after vaccination than after Covid infection, and some demographics—such as girls age 5-11—reported no heart complications following vaccination.

Researchers analyzed electronic health record data from January 1-31 from 40 U.S. healthcare systems participating in the National Patient-Centered Clinical Research Network.

Key Background

Inflammation like myocarditis can be caused by immune response to common pathogens and, in rare instances, to vaccines, Yale pediatric cardiologist Dr. Jeremy Asnes said. In most cases, patients who experienced myocarditis or pericarditis who sought treatment quickly improved with the help of medication and rest, the CDC reported. In 2021, the public collapses of apparently healthy young male athletes—such as Danish soccer player Christian Eriksen and U.S. basketball player Keyontae Johnsonraised concerns that vaccine-induced cardiac side effects might have been to blame. However, investigations into these and other athlete collapses unearthed no evidence linking the incidents to vaccines. Sudden cardiac death is relatively common among athletes, affecting about 1 in 40,000 to 1 in 80,000 athletes annually, according to a 2016 study published by the National Library of Medicine, which found sudden cardiac death to be the most common medical cause of death among athletes. Nonetheless, this rare association between vaccines and usually mild cardiac reactions has been spun by conspiracy theorists into wild claims of dozens of vaccine-caused heart attack deaths among athletes. In 2021, the CDC launched an ongoing investigation into incidences of heart inflammation that were first detected among teenage boys who had received Pfizer or Moderna’s vaccines, but continues to recommend that everyone age 5 and older be vaccinated. This recommendation is reinforced by Friday’s study, indicating that people in all age groups currently eligible for the vaccine are at a lower risk of heart complications after getting vaccinated than after catching Covid.

Tangent

Johnson & Johnson and Janssen’s Covid vaccine, which uses traditional, non-mRNA technology, has not shown the same pattern of rare cardiac side effects as Pfizer and Moderna’s vaccines. However, Johnson & Johnson’s vaccine carries a small risk of causing serious blood clots and is less effective at preventing Covid than Pfizer and Moderna’s vaccines, which has led the CDC to prefer Pfizer and Moderna’s vaccines in most contexts.

Further Reading

“New Covid-19 Vaccine, Myocarditis Claims From Questionable Abstract In American Heart Association Journal” (Forbes)


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