Exploring the Mystery of COVID-19 Vaccine-Linked Heart Inflammation (Myocarditis Symptoms)

Myocarditis symptoms

Heart inflammation in males (Myocarditis symptoms) 

In exceptionally rare cases, people, typically young males, negatively respond to the mRNA COVID-19 vaccines manufactured by Pfizer-BioNTech and Moderna. These responses include myocarditis, the inflammation of the heart muscle, and pericarditis, which is the inflammation of the sac surrounding the heart muscle. The risk of myocarditis and pericarditis from mRNA vaccines appears mild and temporary, and lower than the risk of the same conditions from COVID-19.

Nonetheless, researchers aren’t sure why the mRNA vaccines appear to, in rare cases, cause this condition. According to the U.S. Food and Drug Administration (FDA), the risk seems higher within seven days of the second jab of the vaccines. In vaccinated individuals, it is typically mild and requires minimal treatment.

The U.S. Centers for Disease Control and Prevention (CDC) indicates that the benefits of preventing COVID-19, hospitalizations, and death from the vaccines outweigh the risks of myocarditis symptoms and pericarditis.

A study published in 1996 notes that, in North America, myocarditis is caused by viral infections “with a wide spectrum of natural history. The majority of patients recover spontaneously, but those with persistent ventricular dysfunction face a 20% one-year mortality. Myocarditis initiates as viral disease, and molecular techniques have confirmed viral persistence.”

The Mayo Clinic adds that myocarditis can result from a drug reaction or part of more general inflammatory conditions. Myocarditis symptoms include chest pain, fatigue, shortness of breath, and rapid or irregular heartbeats.

What Does Studies Depict About Myocarditis Symptoms

In a study conducted by Kaiser Permanente Southern California (KPSC) and published in JAMA Internal Medicine on October 4, 2021, in a cohort of 2,392,924 members of KPSC who had received at least one dose of COVID-19 mRNA vaccines, there were 15 cases of confirmed myocarditis symptoms, two after the first dose and 13 after the second. This is an observed incidence of 0.8 cases per 1 million first doses and 5.8 cases per 1 million second doses over a 10-day observation window. All were males with a median age of 25 years.

A CDC study cites rates of about 12.6 cases per million doses of second-dose mRNA vaccine in people 12 to 39 years of age. The patients typically reported chest pain two to three days after a second dose and had elevated cardiac troponin levels. ECG was abnormal.

The authors of the study say this warrants further investigation and note that “no relationship between COVID-19 mRNA vaccination and postvaccination myocarditis can be established given the observational nature of this study.”

According to a CDC study, from March 2020 to January 2021, the risk of myocarditis was 0.146% in patients diagnosed with COVID-19 during an inpatient or hospital-based outpatient encounter and 0.009% in patients not diagnosed with COVID-19. Another way of putting it is that the risk myocarditis symptoms showed was 15.7 times higher for people with COVID-19 than healthy people.

Some theories as to why the mRNA vaccines might cause myocarditis revolve around the spike protein. In the SARS-CoV-2 virus, which causes COVID-19, the spike protein helps the virus enter human cells then take over the cell’s genetic machinery to reproduce itself. The mRNA vaccines code for segments of the spike protein, which then trains the immune system to recognize the spike protein and thus recognize the virus.

Another theory, according to Biykem Bozkurt, M.D., Ph.D., a professor of medicine specializing in cardiology at Baylor College of Medicine in Houston, says there might be similarities between the spike protein and proteins in the heart muscle. This is dubbed the “molecular mimicry” theory, but it hasn’t been fully tested in people who have been vaccinated and doesn’t explain why myocarditis symptoms aren’t seen more broadly.

Jay Schneider, M.D., Ph.D., a consultant in cardiovascular medicine at the Mayo Clinic’s Jacksonville, Fla., campus, speculates that some of the mRNAs in the vaccines might be taken up by cardiomyocytes, which are specialized heart cells. They then manufacture the spike protein, which could stimulate an antibody response against the cells. Schneider got heart cells to take up the Moderna vaccine in laboratory studies and then express the spike protein. Those results haven’t been published yet, and Schneider is cautious about the interpretation.

Yet another theory is that improper injection of the vaccines might be a factor. The injections should be into the deltoid (shoulder) muscle. But if the injection is accidentally into a vein, some of the vaccines might be delivered to the heart via blood vessels. A research study in Hong Kong that injected mice intravenously with the Pfizer-BioNTech vaccine resulted in both myocarditis and pericarditis in the animals.

And yet another theory focuses on the fact that myocarditis symptoms only seem to appear in male adolescents and young men. Bozkurt suggests that testosterone may play a role by increasing an inflammatory immune response. Alternately, Bozkurt notes in a study published in Circulation that underdiagnosis of cardiac disease in women may also be a factor.

Studies have hinted that the Moderna vaccine has a higher risk of showing myocarditis symptoms than the Pfizer-BioNTech. The difference hasn’t been confirmed, but the Moderna vaccine is given at a higher dose than the Pfizer-BioNTech vaccine, and Moderna’s chief executive officer Stéphane Bancel noted that if the difference is real, the dosing might be a factor. Some immunologists and vaccine experts have said the dose difference is probably one reason the Moderna vaccine is slightly more effective against COVID-19 with more durability than the Pfizer-BioNTech vaccine.

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