New Research: Your Choice of COVID Vaccine Can Increase Your Risk of Myocarditis

COVID-19 Vaccines Compared

According to cardiologist Guy Witberg, the study is reassuring for vaccine safety.

The study found that Moderna had greater rates of heart inflammation than Pfizer, although the overall risk remained extremely low.

In comparison to the Pfizer BioNTech COVID-19 vaccine, the Moderna Spikevax COVID-19 vaccine has a two- to three-fold greater incidence of myocarditis, pericarditis, or myopericarditis following a second dose; nonetheless, overall cases of heart inflammation with either vaccine are very rare. Males under 40 who got the Moderna vaccine had the greatest incidence of myocarditis, according to the research, which, according to the scientists, may have consequences for choosing certain vaccines for particular populations.

The findings were recently published in the Journal of the American College of Cardiology.

Pfizer BioNTech (BNT162b2) and Moderna Spikevax (mRNA-1273) are the two mRNA COVID-19 vaccines that have been given approval for usage, and as of March 20, 2022, more than 52 million doses of Pfizer and 22 million doses of Moderna have been given in Canada, where this study was conducted. Clinical trials have shown that the vaccines are safe, and monitoring of vaccinated people has shown that side effects are minor and disappear on their own. However, both vaccines have been associated with some rare but serious side effects, most notably myocarditis (inflammation of the heart).

While several studies have been done on each vaccine, few have been done to directly compare the two mRNA vaccines’ safety. The purpose of this research was to compare the risks of myocarditis, pericarditis, and myopericarditis associated with the Pfizer and Moderna COVID-19 vaccines.

People in the study were 18 years old or older and had received two primary doses of either Pfizer or Moderna vaccine in British Columbia, Canada, with the second dose between January 1, 2021, and September 9, 2021. Individuals whose first or second shots were administered outside of British Columbia or had a history of myocarditis or pericarditis within one year prior to the second dose were excluded.

In all, more than 2.2 million second Pfizer doses were given and more than 870,000 Moderna doses. Within 21 days of the second dose, there were a total of 59 myocarditis cases (21 Pfizer and 31 Moderna) and 41 pericarditis cases (21 Pfizer and 20 Moderna). Researchers also looked at rates per million doses and the rate was 35.6 cases per million for Moderna and 12.6 per million for Pfizer—an almost threefold increase after Moderna shots vs. Pfizer. Comparatively, rates of myocarditis in the general population in 2018, were 2.01 per million in people under age 40 and 2.2 per million in people over age 40.

Rates of myocarditis and pericarditis were higher with the Moderna vaccine in both males and females between ages 18 and 39, with the highest per million rates in males ages 18-29 after a second dose of Moderna.

According to the authors, the findings support recommending certain populations receive certain vaccines to maximize benefits and minimize adverse events.

“Few population-based analyses have been conducted to directly compare the safety of the two mRNA COVID-19 vaccines, which differ in important ways that could impact safety,” said Naveed Janjua, MBBS, DrPH, lead author of the study and an epidemiologist and the executive director of Data and Analytic Services at the British Columbia Centre for Disease Control. “Our findings have implications for strategizing the rollout of mRNA vaccines, which should also consider the self-limiting and mild nature of most myocarditis events, benefits provided by vaccination, higher effectiveness of the Moderna vaccine against infection and hospitalization [found in prior studies], and the apparent higher risk of myocarditis following COVID-19 infection than with mRNA vaccination.”

Limitations of the study include that it was observational, which limits the ability to determine causality between vaccination and myocarditis or pericarditis. However, temporality was ensured in the study design to limit the time studied between vaccine dose and myocarditis/pericarditis diagnosis. Also, the study relied on hospital and emergency department visit data and may have missed some less severe cases.

In a related editorial comment, Guy Witberg, MD, MPH, a cardiologist at Rabin Medical Center in Petah-Tikva, Israel, wrote the study is reassuring for vaccine safety since it provides further data that myocarditis is a very rare adverse event after both vaccines, and it is an important step toward a personalized approach to administering COVID-19 vaccines.

“[The study] should help put to rest ‘vaccine hesitancy’ due to concerns over cardiac adverse events,” Witberg said. “This is one of only a few direct comparisons of the two widely adopted mRNA vaccines, and its results have practical policy implications: for a substantial segment of the population suffering from cardiovascular disease…these data give a strong argument to preferentially use the BNT162b2 [Pfizer] vaccine over mRNA-1273 [Moderna].”

References: “Comparative Risk of Myocarditis/Pericarditis Following Second Doses of BNT162b2 and mRNA-1273 Coronavirus Vaccines” by Zaeema Naveed, Julia Li, James Wilton, Michelle Spencer, Monika Naus, Héctor A. Velásquez García, Jeffrey C. Kwong, Caren Rose, Michael Otterstatter and Naveed Z. Janjua, 7 November 2022, Journal of the American College of Cardiology.
DOI: 10.1016/j.jacc.2022.08.799

“A Tale of 2 mRNA Vaccines” by Guy Witberg and Ilan Richter, 7 November 2022, Journal of the American College of Cardiology.
DOI: 10.1016/j.jacc.2022.09.010

The study was funded by the British Columbia Centre for Disease Control and the Canadian Immunization Research Network (CIRN) through a grant from the Public Health Agency of Canada and the Canadian Institutes of Health Research. This project was also supported by funding from the Public Health Agency of Canada through the Vaccine Surveillance Reference Group and the COVID-19 Immunity Task Force.


View Comments

  • Not very surprising to me, a quick search of the ingredients of the three Covid-19 vaccines revealed that the Maderna and Pfizer vaccines contain polyethylene glycol (PEG), a synthetic petroleum based product similar to FDA approved propylene glycol (PG) which I personally unintentionally ingested in combination with cocoa or chocolate (known personal allergen) in common food products, preceding multiple disparate incidents of crippling, painful gout or pseudogout. A little more searching revealed six known cases of allergic reactions to the PEG in the vaccines. While the reported numbers remain small the most important things are that, statistically, Covid-19 never was a serious threat to most healthy young individuals, being vaccinated exposes people to unnecessary risks and none of the vaccines addressed the underlying causes of the preexisting conditions, comorbidities and related/resultant medical errors which actually killed the majority of alleged Covid-19 victims; bad medicine for profit; bad governance by the pawns and puppets of the rich.

  • "nonetheless, overall cases of heart inflammation with either vaccine are very rare"...
    What a damn joke!
    Because so many are DYING, they don't have to worry about inflammation!
    Carrying water for the pharmaceutical industry is not a good thing... But hey, this is "science"...
    To quote you: "nonetheless, overall cases of science being right are very rare!"

  • I have found it interesting that there have been no studies or results of the effects on epilepsy, considering how many million people live with this condition. Both my GP and my pharmacist, in Western world have no info.

  • You buried what should have been the lead.
    “[The study] should help put to rest ‘vaccine hesitancy’ due to concerns over cardiac adverse events,”

  • READ the data, calm down people. Your chances of getting one of the mentioned conditions went from 2:1,000,000 to 30:1,000,000. That's a 0.003% chance.

    "Researchers also looked at rates per million doses and the rate was 35.6 cases per million for Moderna and 12.6 per million for Pfizer—an almost threefold increase after Moderna shots vs. Pfizer. Comparatively, rates of myocarditis in the general population in 2018, were 2.01 per million in people under age 40 and 2.2 per million in people over age 40."

  • I was hospitalized 2 weeks after my 2nd shot they were notified about the the forced vacation but no kind of study info

  • As commenter Charles G. Shaver already pointed out, COVID was not a lethal threat to most people, unless you were already severely immune compromised (like being treated for cancer w/ chemo, or unmanaged HIV infection, or being morbidly obese) or elderly & frail.

    So why would any healthy individual under 40 want these shots, that come with a so-called "rare"--- but extremely real & potentially life changing chance of heart damage.

    Myocarditis is never mild or self-limiting. Your heart cannot repair itself. If your heart becomes inflammed enough, those cells just die and they become scar tissue. Which make it harder for the heart to operate like it used to. Not just expanding and contracting-- its also harder for the electrical signals to pass through the heart. I guess scar tissue isn't very conductive.

    The saddest part is just how difficult it is for these vaccine injured folks to get a proper diagnosis for their chest pain & basic acknowledgment from the medical community & the govt that this tragedy happened to them, through no fault of their own. Instead of helping these poor victims, they are dismissed as crazy, prescribed SSRI's for "pandemic-related anxiety & depression", given ibuprofen for chest pain, and sent home to cry.

    Join one of the online support groups. These folks are miserable. Their docs won't listen. They don't think it's possible this could be caused by the safe & effective vaccine.

    And yet these patients have had their lives turned upside down. They can't work, they can't do chores around the house, they can't watch their kids, some of them can't even eat without causing a painful flare!

    Mandates must be overturned immediately before any more people get hurt. The injections were never testing for stopping the spread so there is no justification for mandates on behalf of "the greater good".

    Healthy young individuals should not take these shots. It makes no sense. The benefits can never outweigh the harms of the vaccine, when COVID is not a threat to that age group in the first place.

  • Re: Title of the article....

    Remember when govt insisted this was such an emergency that we all had to get the first shot that was offered to us? don't you dare ask any questions or compare efficacy across brands or side effects profiles?!

American College of Cardiology

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