Pfizer Identified ‘Most Likely’ Mechanism for Heart Inflammation After COVID-19 Vaccination

A health care worker prepares a dose of Pfizer BioNTech COVID-19 vaccine in a file image. Ezra Acayan/Getty Images

Pfizer examined possible ways its COVID-19 vaccine causes heart inflammation, a newly disclosed document shows.

The company, in a 2022 white paper, acknowledged that its vaccine, BNT162b2, may be causing myocarditis—which is heart inflammation—and a related condition called pericarditis. Pfizer scientists claimed that the inflammation likely wasn’t the result of direct cardiotoxicity but didn’t rule out several other possible mechanisms, including that it stemmed from immune activity.

The immune system may be triggered by lipid nanoparticles that, in the messenger RNA (mRNA) shot, deliver the spike protein, the document says.

“Although the BNT162b2 mRNA vaccine is optimized to reduce its detection by the innate immune system through the addition of nucleoside modifications and minimizing double-strand RNA impurity, it is possible, especially in certain individuals with genetic predisposition and underlying conditions that the immune responses to mRNA may not be sufficiently turned down and drive the activation of an innate and adaptive immune response,” the scientists wrote in the white paper.

“This may lead to the excessive activation of proinflammatory cascades which contribute to the development of myocarditis,” they wrote.

Myocarditis is a serious condition that can be deadly for some people. Many occurrences after COVID-19 vaccination have been in healthy, young people, with young males particularly at risk. The incidence is as high as 78.7 per million second doses in males aged 16 or 17, according to reports to the Vaccine Adverse Event Reporting System, with several dozen cases being reported after the second dose among 12- to 15-year-old and 18- to 24-year-old males.

Myocarditis also is an issue after booster vaccination, data from the United States and other countries show.

The U.S. Centers for Disease Control and Prevention is among the entities that have said the evidence shows the Pfizer and Moderna COVID-19 vaccines cause myocarditis.

‘Has Not Been Made’

In the February 2022 paper, obtained and published by Project Veritas, Pfizer employees say that the company hadn’t defined myocarditis as an adverse reaction to its vaccine, meaning it hadn’t agreed that its vaccine causes myocarditis. It claimed that the benefits of the vaccine outweigh the risks, but a growing number of experts disagree, especially for young people.

Pfizer didn’t respond to requests for comment, including whether it has changed its stance on myocarditis in the intervening time.

Pfizer scientists used similar language to that used publicly by the company, acknowledging that there had been “increased cases of myocarditis and pericarditis” after mRNA COVID-19 vaccination. They claimed that most people recovered, but studies show myocarditis has long-term effects for some patients. Myocarditis has killed some people.

The scientists also noted that the true number of myocarditis cases after vaccination “is likely underestimated” because it can be difficult to assess milder cases.

Possible Mechanisms

Scientists are still trying to figure out how the mRNA shots cause heart inflammation.

In the paper, Pfizer scientists said the “most likely” mechanism was immune-mediated. The lipid nanoparticles, they said, may activate immune responses. The nanoparticles could also lead to the development of autoantibodies, or antibodies that attack a person’s immune system, they said, pointing to the case of a 52-year-old man who developed myocarditis that may have involved the generation of autoantibodies.

Cardiologist Dr. Peter McCullough reviewed the paper. He told The Epoch Times via email that the lipid nanoparticles in the mRNA shot are “widely distributed in the body in the circulation for a month or more,” which “allows myocardial blood flow to repeatedly bathe the heart with vaccine products activating systemic and tissue immune response.”

Researchers have detected mRNA in the blood weeks after vaccination.

A third possible mechanism is molecular mimicry, or the introduction of antigen structures that appear similar to but aren’t, normal human structures, making it difficult for the immune system to properly classify them.

Pfizer scientists undertook a study to look at whether certain proteins that contain peptides, or a series of amino acids, could lead to immune responses triggered by the vaccine to “cross react with human proteins.” They identified several with 100 percent similarity to human proteins, but neither is “expressed predominantly in the heart.” Another six proteins were identified with algorithms, and one, nebulette, “has a heart-specific expression profile and may be involved in cardiac myofibril assembly.” Testing is needed to determine whether nebulette leads to cross-reactivity, the scientists said.

They ruled molecular mimicry an “unlikely mechanism.”

Malone’s View

Dr. Robert Malone, who helped develop the mRNA technology, said that lipid nanoparticles do activate the human immune system and that the RNA in the vaccine leads to inflammatory responses in the cells and tissues.

“This strong proinflammatory response of the mRNA/lipoplexes is the reason I (and others including [biotechnology company] Genzyme) abandoned further research into this technology in the late 1990s and turned to other delivery methods such as direct (‘naked’) injection and use of pulsed electrical fields,” Malone told The Epoch Times via email.

“It is reasonable to hypothesize that such proinflammatory processes might damage heart and other tissues. One key risk factor for COVID disease, and potentially for the post-vaccination syndrome, is a proinflammatory state such as is seen with both diabetes and pre-diabetes. That’s also consistent with this hypothesis,” he said.

Cardiotoxicity from the spike protein, which has been shown to linger in the body for weeks or even months after injection with the vaccine, is one possible mechanism for myocarditis.

“What we can conclude is that spike is a protein is a toxin. It acts through multiple mechanisms. One of those mechanisms appears to be eliciting a variety of autoimmune phenomena,” Malone said. “It’s known that viral myocarditis often acts through this autoimmune mechanism. And it’s reasonable to infer that the similar mechanism might be occurring in the case of these vaccines that are eliciting immune response against the virus proteins.”