A peer-reviewed study of 9.2 million South Koreans published in Nature Communications uncovered a 620% increased risk of myocarditis and 175% higher risk of pericarditis following mRNA COVID-19 vaccination. Researchers also noted increased risks of several autoimmune conditions, especially after booster doses.
A large-scale peer-reviewed South Korean study has found significantly increased risks of serious cardiac and neurological conditions following mRNA COVID-19 vaccination, and lesser risks of several autoimmune diseases.
The nationwide population-based cohort study, published Tuesday in Nature Communications, followed nearly 4.5 million people for an average of 15 months after vaccination.
Researchers found a striking 620% increased risk of myocarditis and 175% increased risk of pericarditis in people who received the vaccine compared to historical controls.
The study also revealed a 62% increased risk for Guillain-Barré syndrome (GBS), a rare neurological disorder.
The researchers did not highlight the the cardiac and GBS risks, but only used the data to confirm the validity of their study design, which focused on determining the risks of autoimmune diseases associated with mRNA COVID-19 vaccines.
The researchers found a 16% increased chance of systemic lupus erythematosus (SLE — the most common lupus type) and a 58% higher risk of bullous pemphigoid (BP — large, fluid-filled blisters).
The study also revealed that booster shots were associated with slightly increased risks of several autoimmune connective tissue diseases (AI-CTDs), including alopecia areata (patchy hair loss), psoriasis (scaly, inflamed skin) and rheumatoid arthritis.
“Given that the risk of SLE and BP was increased in certain demographic conditions such as age and sex, long-term monitoring is necessary after mRNA vaccination for the development of AI-CTDs,” the study authors noted.
Brian Hooker, Ph.D., chief scientific officer at Children’s Health Defense (CHD), noted how the authors minimized the most alarming data but told The Defender the study was otherwise “very robust.”
Hooker said several other studies also show relationships between autoimmune disorders — including systemic lupus — and mRNA vaccination.
The Nature Communications article follows another South Korean study published in May that found significant increases in the incidence of Alzheimer’s disease and mild cognitive impairment following COVID-19 mRNA vaccination.
The South Korean study, one of the largest of its kind, examined the long-term risk of autoimmune connective tissue diseases following mRNA-based SARS-CoV-2 vaccination.
Researchers analyzed data from 9,258,803 individuals who had received at least one dose of an mRNA COVID-19 vaccine. The researchers then randomly split this total into a vaccination cohort of 4,445,333 people and a historical control cohort of 4,444,932 individuals.
Because of South Korea’s high vaccination rate (96.6% of adults completed the primary COVID-19 series by October 2022), the researchers studied the health history of the control cohort for the two-year period prior to their first vaccine dose, up to Dec. 31, 2020 — just before the vaccine rollout. The vaccination group was observed through Dec. 31, 2022.
Karl Jablonowski, Ph.D., senior research scientist at CHD, criticized the observation period for the historical control group, pointing out that this timeframe bridges the first year of the SARS-CoV-2 pandemic.
“This makes it impossible (or really darn difficult) to disentangle results based on vaccination or infection,” he told The Defender. “Ideally this study would include a contemporary unvaccinated cohort for scientific examination.”
However, the researchers chose not to study unvaccinated people due to concerns over “inappropriate cohort selection and potential selection bias.”
The mean follow-up times were 471.24 ± 66.16 days for the vaccination cohort and 471.28 ± 66.15 days for the historical control cohort.
The researchers used comprehensive demographic data and healthcare records from the National Health Insurance Service (NHIS) and Korea Disease Control and Prevention Agency (KDCA) databases, which cover over 99% of the South Korean population.
They attributed disease conditions when confirmed by the corresponding International Classification of Diseases (ICD-10) diagnostic codes through at least three inpatient or outpatient visits during the observation period.
To ensure fair comparisons between the vaccinated group and the historical control group, researchers used statistical methods to balance out differences in:
They also accounted for changes over time, such as when people got booster shots.
The researchers used their assessment of increased risks for myocarditis, pericarditis and Guillain-Barré syndrome as “positive control outcomes” to validate their study methodology.
By demonstrating the known increases in risk for these outcomes, the researchers aimed to show that their study design was capable of detecting vaccine-related adverse events.
Negative control outcomes included benign skin tumors, melanoma in situ (stage 0) and tympanic membrane perforation (ruptured eardrum) — conditions less likely to be associated with COVID-19 vaccination.
This approach lends credibility to their findings on autoimmune connective tissue diseases, suggesting that the observed increases in risk for certain AI-CTDs are likely genuine effects rather than artifacts of the study design or analysis methods.
The study identified the following variations in the vaccinated versus unvaccinated groups, respectively:
Hooker told The Defender he found it odd that increased risks for these “control” sequelae were treated in passing. “It’s like, ‘Oh, everyone knows that these vaccines cause myocarditis, pericarditis and GBS … ho hum. If you have that adverse event, oh well, too bad for you.’”
Jablonowski said that given the extreme risk increase of myocarditis from vaccination found in the study, it was “stunning” that neither the paper’s title nor abstract even mentioned it. He attributed the exclusion to “the changing scope of censorship in science.”
He said:
“We know that myocarditis is most often the result of the second mRNA dose. Figure 5 of the paper further verifies this, as column C denotes a 9.17-times increase in myocarditis for those who receive only mRNA vaccinations as opposed to 2.91-times increase in myocarditis for those who are cross-vaccinated with mRNA and non-mRNA vaccines.”
Jablonowski highlighted the paper’s confirmation of other studies showing people younger than 40 are nearly twice as likely to develop myocarditis as those over 40 (12.53 times increased risk versus 6.18 times).
But he was surprised by the study’s findings that females are nearly twice as likely to develop myocarditis as males (10.53 times increased risk versus 5.26 times). “To my knowledge, this has never been shown in any population before.”
Regarding the study’s primary stated purpose, the researchers found that mRNA vaccination did not increase the risk of most autoimmune connective tissue diseases.
However, they identified a statistically significant 16% increased risk of systemic lupus erythematosus in vaccinated individuals when compared to the historic control cohort.
Gender-specific risks also emerged in the analysis. Women receiving the mRNA vaccine had a significantly higher risk — 167% — of developing bullous pemphigoid, compared to just a 2% increased risk for men.
The research also uncovered the following increased risks associated with COVID-19 booster shots: 12% for alopecia areata, 14% for rheumatoid arthritis and 16% for psoriasis.
Differences between vaccine types were also noted. Recipients of the Pfizer-BioNTech BNT162b2 vaccine had an 18% higher risk of developing SLE compared to those who received Moderna’s mRNA 1273 vaccine, who had an 8% increased risk.
Jablonowski said he had no theory about how the two vaccine brands resulted in the different risks observed. He speculated it could have something to do with the timing of the doses, with the two Pfizer doses being recommended three weeks apart and two Moderna doses four weeks apart.
The researchers wrote that the association between mRNA vaccination and SLE remains unclear, but they admitted that vaccine-associated SLE has been found in other studies.
The researchers noted that mRNA vaccines may increase levels of certain antibodies in the blood that can react with the body’s own DNA. This process could potentially trigger autoimmune diseases like lupus.
They also referenced a study suggesting that booster shots may increase the amount of free-floating DNA in key immune cells. This could potentially disrupt normal immune function.
Hooker said that “Mechanisms regarding innate immune activation via DAMPS [damage-associated molecular patterns] have been proposed for these relationships” between mRNA vaccines and autoimmune disorders like SLE. This process involves cells releasing bits of their own DNA and other molecules, causing the immune system to overactivate and potentially attack the body’s own tissues.
The authors called for further research into the association between mRNA-based vaccines and AI-CTDs.
The researchers highlighted several key limitations to their findings.
The study’s focus on a single ethnic group, South Koreans, may limit its applicability to other populations due to genetic variations in autoimmune disease susceptibility.
The authors noted that the two-year pre-study observation period may have missed some pre-existing autoimmune conditions due to their gradual onset.
Requiring three consistent ICD-10-coded records for each person to confirm disease states may also have understated the actual rates.
Pandemic-related reductions in healthcare utilization could have led to the under-diagnosis of some conditions during the study period, they said.
Despite a mean follow-up of 471 days, one of the longest for mRNA vaccine studies, the authors noted this might still be insufficient given the potentially slow development of autoimmune connective tissue diseases.
Hooker emphasized that 15 months is “the tip of the iceberg” for this type of study. He said:
“Autoimmune sequelae could take years to develop, based on previous experience with ASIA (autoimmune / inflammatory syndromes induced by adjuvants). This is confounded by boosters ad infinitum, especially with mRNA vaccines.”
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