Study Finds 9.6% Fatality Rate Among People Who Reported Myocarditis or Pericarditis After an mRNA COVID Vaccine

Nearly 10% of people in Japan who reported having myocarditis or pericarditis after receiving an mRNA COVID-19 vaccine died from the condition within 64 days after they received the vaccine.

by Suzanne Burdick, Ph.D.

Nearly 10% of people in Japan who reported having myocarditis or pericarditis after receiving an mRNA COVID-19 vaccine died from the condition within 64 days after they received the vaccine, a new peer-reviewed study found. Fatality rates were highest among men under 30.

However, the study authors downplayed the finding by reporting that “overall outcomes were good,” according to Dr. Peter McCullough — a cardiologist and author of more than 1,000 publications — who analyzed the study on his Substack.

“In the COVID-19 crisis,” McCullough said, “we have learned to look at the data and the analyses ourselves because there are usually very important results downplayed by the authors — this time it is vaccine myopericarditis mortality.”

McCullough combined the numbers from the study’s results for myocarditis and pericarditis cases to show that 97 of the 1,014 (9.6%) myopericarditis cases were fatal.

Myopericarditis is an umbrella term for myocarditis, inflammation of the heart, and pericarditis, inflammation of the tissue surrounding the heart.

“A 9.6% case fatality rate for a vaccine side effect largely in young healthy men is astronomical and clinically unacceptable,” he said.

McCullough criticized the authors’ conclusion that “overall outcomes were good.”

“This can never be the conclusion when the case fatality rate was 97/1014 cases with followup out to 64 days after the shot,” he said.

The study authors extracted data from April 2004 to December 2023 in the Japanese Adverse Drug Event Report (JADER) — a large database for public reporting of adverse events — among people ages 12 and up who experienced myocarditis or pericarditis after getting an mRNA COVID-19 shot.

Among 759 reports of vaccine-induced myocarditis and 255 reports of pericarditis, 84 (11%) and 13 (5%) individuals died within 64 days of an mRNA COVID-19 shot, respectively.

The study, which is in press, was available online early this month in the Journal of Infection and Chemotherapy.

The Defender reached out to the study’s corresponding author — Kazuaki Taguchi, Ph.D., with the Faculty of Pharmacy at Keio University in Tokyo — for comment about the team’s conclusions but did not receive a response by the deadline.

Japanese males under 30 ‘should promptly seek medical assistance’

Taguchi and his co-authors said they undertook the study to clarify the association between mRNA vaccines and myocarditis/pericarditis.

They concluded that in the Japanese population, COVID-19 mRNA vaccination was “significantly associated with the onset of myocarditis/pericarditis.” They noted that influencing factors included being under 30 years old and male.

Japanese males under 30 should “promptly seek medical assistance for inspection and

treatment upon experiencing chest symptoms after vaccination,” they wrote.

For the study, the authors first looked at adverse event reports to determine how soon after an mRNA vaccination people reported the onset of myocarditis or pericarditis.

The majority of cases occurred within a week of getting the vaccine. They noted that prior studies found a similar trend.

“Considering the results of the present study and previous reports,” they wrote, “it is necessary to pay particular attention to the onset of myocarditis and pericarditis within 7 days after SARS-CoV-2 mRNA vaccination.”

The authors then analyzed the outcome of the myocarditis and pericarditis cases — such as full recovery, remission, ongoing or increased symptoms, or death.

Among the cases they analyzed, half of the people who reported getting pericarditis and nearly half (47%) of those who reported getting myocarditis recovered, they said.

Another 37% and 31% of pericarditis cases and myocarditis cases, respectively, reported being in “remission.”

They noted a “severe outcome” or “non-recovery” — but not death — occurred in 8% (20) of the pericarditis cases and 11% (80) of the myocarditis cases. As noted earlier, death occurred in 11% of the myocarditis cases and 5% of the pericarditis cases.

The authors appeared to not investigate the amount of time between onset and outcome. Also, because they examined myopericarditis cases that occurred between one and 64 days after vaccination, their study didn’t report on changes in outcome — such as improvement or worsening in symptoms — that happened more than 64 days post-vaccination.

The Japanese study received no funding from any government agency, for-profit or nonprofit group.

‘These data are just the tip of the iceberg’

According to McCullough, “These data are just the tip of the iceberg,” as prior studies suggest the risk of heart damage goes up roughly 2.5% with each successive booster and that half of myopericarditis cases may be subclinical, meaning asymptomatic.

The Japanese study looked only at the reports from symptomatic myopericarditis cases.

Taguchi and his co-authors said they couldn’t analyze the relationship between the number of vaccinations and the risk of myocarditis/pericarditis “due to the difficulty in determining the timing of the dose.” They called for more research.

McCullough said the Japanese data may not accurately show all cardiac harm caused by mRNA COVID-19 vaccines because some subclinical myopericarditis cases may only manifest later on — beyond the study’s 64-day window of inquiry — as cardiomyopathy, heart failure or sudden death.

Cardiomyopathy is a disease of the heart muscle that causes the heart to have a harder time pumping blood to the rest of the body, which can lead to symptoms of heart failure, according to the Mayo Clinic.

CDC fails to mention risk of death from vaccine-induced myopericarditis 

McCullough pointed out that the Centers for Disease Control and Prevention’s (CDC) official guidance to U.S. healthcare practitioners regarding myopericarditis in teens and young adults after receipt of a COVID-19 vaccine fails to mention that the condition can be fatal.

The CDC’s Clinical Considerations website states:

“The severity of myocarditis and pericarditis cases can vary; most patients with myocarditis after mRNA COVID-19 vaccination have experienced resolution of symptoms by hospital discharge.”

McCullough said, “Hospitalization is a concerning outcome for any young person after taking a vaccine that should be safe and have a meaningful health benefit.”

The CDC’s Myocarditis and Pericarditis After mRNA COVID-19 Vaccination website similarly neglects to mention that the condition can be fatal.

The Defender asked the CDC if it plans to update the website by notifying the public about the risk of fatality but did not receive a response by the deadline.