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Home » Myocarditis and COVID mRNA vaccines – very rare adverse event

Myocarditis and COVID mRNA vaccines – very rare adverse event

Last updated on August 17th, 2021 at 01:08 pm

Regulatory agencies, such as the FDA and CDC, are monitoring reports of myocarditis, a heart inflammation, after COVID-19 mRNA vaccines from Moderna and Pfizer. Although myocarditis after these vaccines are exceedingly rare, anti-vaccine activists have already jumped on this issue to make it appear that COVID-19 vaccines are dangerous.

My job is to look at this data and give you a scientific analysis of the observations and whether they are actually related to the vaccine.

Like with reports of other conditions, such as blood clots, after receiving COVID-19 vaccines, we need to examine whether myocarditis is actually related to the vaccine or just random events in which the incidence is no different than what would be predicted in a similar group of unvaccinated people. And if it is linked, we need to look at the potential risk and compare it to the risks of COVID-19 itself.

COVID-19 vaccines myocarditis
Photo by Robina Weermeijer on Unsplash

What is myocarditis?

Simply, myocarditis, also known as inflammatory cardiomyopathy, is a very rare inflammation of the heart muscle. Symptoms may include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. The duration of the condition can vary from hours to months. Complications of myocarditis may include heart failure due to dilated cardiomyopathy or cardiac arrest.

Most of the time, myocarditis is caused by an infection that reaches the heart. When it does, the immune cells that fight the infection enter the heart. These immune cells produce biochemicals that can damage the heart muscle. Consequently, the heart itself can become thick, swollen, and weak.

Many of the cases are caused by a virus that reaches the heart. These can include influenza virus (flu), coxsackieviruscytomegalovirus, adenovirus, and others. The condition may also be caused by bacterial infections such as Lyme disease, streptococcus, mycoplasma, and chlamydia.

As you can see, some sort of infectious pathogen, such as viruses and bacteria, are almost always implicated in the etiology of myocarditis. And remember, all of the COVID-19 vaccines do not contain live SARS-CoV-2 virus, they only have a piece of code for the spike protein of the virus.

In vast majority of cases, the effects are temporary, and the condition resolves itself.

Myocarditis and COVID-19 mRNA vaccines

In early June, the CDC issued a note to healthcare providers raising awareness of myocarditis and pericarditis after vaccination, particularly in younger males. That guidance stated that, since April, there’s been an increase in reports of myocarditis and pericarditis (an inflammation of the sac around the heart – infections are also implicated) after receiving Pfizer or Moderna COVID-19 mRNA vaccines. The CDC said the cases typically occurred within four days after receiving the mRNA vaccines.

Myocarditis and pericarditis have not been reported after the JNJ COVID-19 vaccine, so this is just an issue with the mRNA COVID-19 vaccines.

This follows a 17 May 2021 report from the CDC’s Advisory Committee on Immunization Practices (ACIP) COVID task force that they were examining reports that a few young, predominantly male, vaccine recipients, who had received either the Pfizer or Moderna mRNA vaccines, had developed myocarditis.

ACIP met on Wednesday, 23 June 2021, to discuss instances of myocarditis or pericarditis in people aged 30 and younger who have received either of the mRNA COVID-19 vaccines.

Although the cases are very rare, the rate at which they are occurring in the age range of 16 to 24 years is slightly above what is typically expected in the population.

The meeting began with an overview of COVID-19 cases in the United States, the safety of mRNA vaccines, and cases of myocarditis or pericarditis after vaccination.

The CDC have confirmed 323 cases of myocarditis or pericarditis in individuals aged 29 years and younger from the Vaccine Adverse Event Reporting System (VAERS). Of those, 309 were hospitalized, with 295 of them eventually being discharged. Of the remaining, 9 are still in the hospital, of which 2 are in the intensive care unit (ICU), and 5 have no outcome data.

As I have long discussed with deep diving into VAERS data, it has a huge number of limitations. First, none of these reports can establish causality between the COVID-19 vaccines and myocarditis. Second, most of the reports do not have information on other conditions that may be linked to myocarditis. So, VAERS can provide an “early warning system” to potential issues, which scientists call “safety signals.”

Following the overview, the COVID-19 Vaccine Safety Technical (VaST) Work Group gave an assessment.

According to VaST, the relatively few reports of myocarditis to date have occurred predominantly in adolescents and young adults, more often in males, more often following the second dose and most have typically occurred within 1 week of vaccination.

The majority of the patients’ symptoms lasted only a short time, with most experiencing rapid resolution of laboratory abnormalities and brief stays in the hospital.

The group stated that the data suggests a likely association of myocarditis with mRNA vaccination in adolescents and young adults. Therefore, VaST will continue to review the data on myocarditis and pericarditis from available surveillance systems, as well as ongoing safety evaluations and will update the ACIP on a regular basis.

After the VaST assessment, a benefit-risk discussion took place which determined that the benefits of mRNA vaccinations still clearly outweigh the risks in adolescents and young adults.

Following the ACIP review of these adverse events, the FDA has decided to make the following recommendations:

  • Those with pericarditis prior to vaccination can receive any FDA authorized COVID-19 vaccine.
  • Those with pericarditis after the first dose of an mRNA COVID-19 vaccine but prior to a second dose should proceed with a second dose of mRNA COVID-19 vaccine after resolution of symptoms.
  • Those with myocarditis prior to a COVID-19 vaccination can receive any FDA-authorized COVID-19 vaccine if their heart has recovered.
  • Those with myocarditis after the first dose of an mRNA COVID-19 vaccine but prior to a second dose should defer a second dose of mRNA COVID-19 vaccine until more information is known. However, if their heart has recovered, they should consider proceeding with a second dose under certain circumstances.

Israel’s response

Additionally, Israel’s Health Ministry is also investigating a small number of cases of myocarditis in people who had received Pfizer’s COVID-19 vaccine, though it has not yet drawn any conclusions..Israeli health regulators said that there have been a small number of myocarditis cases seen mainly among men ages 16 to 30 that may be linked to Pfizer’s COVID-19 vaccine.

Israeli public health officials have seen 275 cases of myocarditis from December 2020 to May 2021 among more than 5 million vaccinated people, according to Reuters. Most of these patients spent no more than 4 days in the hospital, and 95% of cases were classified as mild. The association appeared strongest among men ages 16 to 19 and was more common after the second dose, regulators said.

Nevertheless, Israel still proceeded to authorize the vaccine for 12- to 15-year-olds despite the myocarditis reports.

The VAERS data indicates that around 2 out of 100,000 may develop this condition. However, published studies show that the risk of myocarditis in the general population is around 22 out of 100,000. In other words, and I cannot stress this enough, the risk of myocarditis is over 10 times greater in the general population than it is in the vaccinated population.

No, this data does not imply that the vaccine reduces one’s risk of myocarditis, although COVID-19, being a serious infection, has been linked to myocarditis.

COVID-19 vaccines myocarditis
Photo by Alexandru Acea on Unsplash


Let me repeat myself – the risk of myocarditis from the vaccine is still substantially lower than the risk of death from COVID-19 – 1000-2000 people die out of 100,000 cases, nearly 1000X greater than the risk of myocarditis from the vaccine.

I know that humans have a hard time assessing risk, but all medical procedures have some level of risk. I like to tell the story that reducing a fracture of the arm carries with it some level of risk of death. Yet no one would refuse fix that fracture.

Contracting myocarditis after getting the vaccine is a real, but vanishingly rare event. Dying from COVID-19, no matter how much you believe it won’t harm you, is 1000X more risky.

Finally, even though myocarditis may sound like a dangerous thing, it is not. Effects from the condition are short-term and is not fatal, unlike COVID-19 itself.

And one more thing – this shows how careful regulatory agencies like the FDA and CDC are with all vaccines. They are constantly monitoring safety signals from all across the world to make sure that our vaccines are safe and effective. This just doesn’t happen with the COVID-19 vaccines, but with all of them on the market.

Do not avoid these vaccines because you think that you may get some terrible disease of the heart. No, there is a tiny risk of myocarditis, which almost always resolves itself. Ignore the myths of the anti-vaccine activists – the vaccine is safe and effective.



Michael Simpson

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