People who received one dose of an mRNA COVID-19 vaccine had a higher risk of acute heart disease compared with those who received one dose of a non-mRNA COVID-19 shot, according to a new peer-reviewed study.
A team of South Korean researchers, who published their report on Oct. 24 in Epidemiology and Infection, said the heightened risk was most pronounced among people ages 10 to 59 compared with those age 60 and older.
The study authors analyzed the health data of 3,350,855 people who received one dose of a COVID-19 vaccine from February 2021 to March 2022. The authors obtained the data from South Korea’s National Health Insurance Service (NHIS).
South Korea administered five types of COVID-19 vaccines: the Pfizer-BioNTech and Moderna mRNA shots, and the AstraZeneca, Janssen (Johnson & Johnson) and Novavax non-mRNA shots.
The study authors wanted to see if receiving a first dose of a particular type of COVID-19 vaccine was associated with developing acute heart disease within 21 days post-vaccination.
They also sought to determine if developing a COVID-19 infection within 21 days after the first vaccine dose was linked to a higher risk of acute heart disease.
To find out, they analyzed cardiac adverse events “including acute cardiac injury, acute myocarditis, acute pericarditis, cardiac arrest, and cardiac arrhythmia, in relation to vaccine type and COVID-19 within 21 days after the first vaccination date,” according to their report.
“The results revealed higher heart disease risk in individuals receiving mRNA vaccines than other types,” they wrote. “Individuals infected by SARS-CoV-2 also exhibited significantly higher heart disease risk than those uninfected.”
The study authors didn’t find a statistically significant interaction between individuals’ COVID-19 infection status and the type of COVID-19 vaccine they received — meaning the higher risk wasn’t contingent on the person having both a COVID-19 infection and an mRNA vaccination.
However, they did find that younger people who received mRNA vaccines had a higher heart disease risk compared to those 60 and up.
Dr. Peter McCullough, who posted the South Korean study on his Substack, said public health agencies never studied the comparative safety of the different COVID-19 vaccine types.
There should be “investigations into why the agencies preferentially promoted mRNA vaccines despite their higher risk of cardiovascular events,” McCullough added.
Karl Jablonowski, Ph.D., a senior research scientist at Children’s Health Defense , told The Defender that “overall” the study was “compelling.” He said:
“Elevated risk of acute heart disease for mRNA products over others is biologically plausible, even beyond the well-established myocarditis and pericarditis.
“This study highlights the potential for a population-based approach to reveal such harms.”
Authors call for more research
The authors said their study had some limitations. For instance, they only looked at cardiac adverse events reported during the three weeks following the first vaccination dose.
They explained why they had to do this:
“In our analysis, an adverse event related to the vaccine was considered to be a new acute heart disease-related diagnosis occurring within 21 days of the first dose vaccination date.
“This operational definition was necessary because we lacked information on the specific association between COVID-19 vaccines and diagnostic codes in the NHIS COVID-19 database.
“Given that the recommended interval between the first and second vaccine doses for Pfizer/bioNTech was 21 days, we concentrated on infections occurring within 21 days after the initial vaccine dose.”
It would have been “particularly useful,” they said, if their study could have looked at cardiac adverse events following the second dose. Other recent studies have shown the risk of myocarditis and pericarditis to be highest after the second dose of mRNA vaccines.
They called for more research.
Jablonowski said the study’s results might be skewed due to “the very difficult dimension of time.”
“The authors do an incredible job with the data they have,” he said. “But if not all vaccine types were available at the same time, you’re going to introduce a temporal bias.” He added:
“The authors could have plotted a chart that showed the administration of vaccination type over time — and even overlayed that with disease incidence of COVID-19 infection and the heart diseases under inspection.
“Such a plot may demonstrate how susceptible the study is to temporal bias.”
South Korean government funded the study via a National Research Foundation of Korea grant.
The study’s corresponding author did not immediately respond to The Defender’s request for comment.