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Home » COVID-19 vaccines and myocarditis – what are the facts

COVID-19 vaccines and myocarditis – what are the facts

Regulatory agencies, such as the FDA and CDC, are monitoring reports of myocarditis, a heart inflammation, after COVID-19 vaccines. Although if there is a link, it is exceedingly rare, anti-vaccine activists have already 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 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 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.

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.

Using VAERS data, there were 475 reports of myocarditis and pericarditis in people age 30 and under, 226 of which have met the CDC’s working case definition for the adverse. Preliminary data suggest that most patients (at least 81%) made a full recovery.

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.”

However, a safety signal does not imply or suggest causality. To determine causality, researchers require better data that allows them to compare data between vaccinated and unvaccinated groups. This can help them determine if there is a statistically significant risk.

The CDC monitoring systems have not found more cases than would be expected in the general unvaccinated population. However, members of ACIP felt that healthcare providers should be made aware of the reports of the “potential adverse event.”

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 is over 10 times higher in the general population than in the population that received the Moderna or Pfizer COVID-19 vaccines. Furthermore, the risk of death from COVID-19 1000-2000 out of 100,000, nearly 1000X greater than the risk of myocarditis.

Here’s what we can conclude from these reports:

  1. The CDC is carefully monitoring adverse events after the COVID-19 vaccine, which is why it picked up a potential safety signal in myocarditis after COVID-19 vaccines.
  2. Although there appear to be more reports of myocarditis, the levels are not statistically higher than what is observed in the general unvaccinated population.
  3. Myocarditis, although it sounds like a scary disease, is not deadly in most cases and symptoms resolve after a short period of time, quickly getting better with a full recovery.
  4. Myocarditis was observed more frequently in younger males after receiving the second dose of the mRNA COVID-19 vaccines.
  5. Importantly, myocarditis probably is unrelated to the vaccine, but even if it is, the incidence is much lower than the incidence of dying from COVID-19.

I will be monitoring this story if it develops any further, but I just don’t see where there is a link between the COVID-19 vaccines and myocarditis. However, like with all vaccines, the CDC, FDA, and other regulatory agencies across the world carefully monitor safety signals, and if they can show an actual link, they will quickly tell everyone.



Michael Simpson

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