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A new study linking COVID-19 vaccines to a significantly lower risk of heart attack and stroke joins “the latest in a growing body of research about the vaccine’s benefits for heart health,” according to The Washington Post, which reported on the study.
But Dr. Vinay Prasad, a professor of epidemiology and biostatistics at the University of California, San Francisco, called the study “hopelessly flawed.”
Prasad, the former director of the U.S. Food and Drug Administration’s (FDA) Center for Biologics Evaluation and Research before stepping down in April, and other scientists said the study’s methodological flaws skewed its findings.
“Not only should it not be in the news, the paper should not be in print,” Prasad wrote on Substack.
Canadian researcher Denis Rancourt, Ph.D., called the paper “outright bad science” that “should not be used whatsoever to ‘help inform clinical and public health discussions’ as they propose.”
The study, published last week in JAMA Internal Medicine, tied COVID-19 vaccination to a 37.7% lower risk of serious cardiovascular conditions, particularly among people 75 and older or people with comorbidities.
The authors also found that the vaccinated had a 6.2% lower risk of serious heart conditions overall and a 6.6% reduction in all-cause hospitalizations.
“Extrapolating these estimates to a population of 1 million people, vaccination could plausibly be associated with averting approximately 2370 [major cardiovascular] events and 1580 deaths over an 8-month period,” the study claims.
However, the researchers acknowledged that “the absolute benefit” of COVID-19 vaccination “was modest for the general cohort.”
Heart conditions such as myocarditis are widely associated with the mRNA COVID-19 vaccines, with reports of deaths connected to the vaccines, particularly among teenage and young adult males.
Study lacked true unvaccinated control group
The study observed nearly 1.04 million veterans who used the U.S. Department of Veterans Affairs healthcare system during the 2024-25 cold and flu season.
The researchers compared the health outcomes of those who took the seasonal flu vaccine — a group the researchers classified as “unvaccinated” — and those who received that season’s flu and COVID-19 shots on the same day.
The researchers followed up with the participants after eight months to assess their risk of a major cardiovascular event.
Rancourt said the study’s design was likely to produce outcomes tainted by the healthy vaccinee effect — where the vaccinated group is drawn from people more likely to be in better overall health compared to people who are seriously ill, suffering from comorbidities or near the end of their lives.
“The study is not a controlled trial,” Rancourt said. “No randomization was applied. The unfiltered voluntary vaccination of the subjects is the opposite of randomization. The study uses circumstances that must be expected to produce a large healthy vaccinee bias that is virtually impossible to mitigate.”
The study’s authors “do not mention healthy vaccinee bias in their ‘Strengths and Limitations’ section, nor do they provide any evidence or analysis supporting their unjustified belief that healthy vaccination bias does not invalidate their results,” Rancourt said.
Epidemiologist M. Nathaniel Mead, a McCullough Foundation scholar, said the study had an “invalid control group, which appears to have been unhealthier, more frail or vulnerable to heart problems at baseline.”
In an analysis posted on Substack, French scientist Hélène Banoun, Ph.D., noted that the study lacked a true unvaccinated group.
“It is a comparison between those who received only the flu vaccine and those who received both the flu vaccine and the COVID-19 vaccine on the same day. Therefore, it is not a comparison between vaccinated and unvaccinated individuals,” Banoun wrote.
Banoun noted that some study participants received the COVID-19 vaccine after the flu vaccine but were nevertheless included in the “unvaccinated” group.
“Those who experienced cardiovascular adverse events following a COVID-19 vaccine received shortly afterward (most often 1 to 2 months later) are classified as UNVACCINATED,” Banoun wrote. She noted that the study’s supplemental data show that adverse events are, in fact, “higher among the ‘vaccinated’ group.”
Mead noted that the prior vaccination status of the study’s subjects is unknown. He said:
“We don’t know how many vaccines the ‘unvaccinated’ group had received prior to the study period.
“The ‘no-vaccine arm’ could easily have received multiple synthetic mRNA inoculations prior to the study period, the researchers do not consider the likelihood that the COVID infections are interacting with the persistent spike protein production from those previous COVID mRNA shots to cause heart damage.”
Studies have shown that the mRNA COVID-19 shots contain lipid nanoparticles, which distribute the spike protein to vital organs, including the heart. A study published in the journal Vaccines earlier this year found that the FDA underestimated the risk of heart damage from Moderna’s mRNA shot.
Mead said it’s possible some of the subjects in the “unvaccinated” group could have plausibly sustained an adverse event following receipt of a previous COVID-19 shot, leading them to avoid further COVID-19 shots.
“If the ‘no vaccine’ group had in fact received multiple shots prior to the study period, this would have resulted in persistent spike protein in the blood that could have predisposed them to more cardiac issues following the infection … as my colleagues and I convincingly argued in our compound adverse events papers,” Mead said.
Study contained several statistical anomalies
Experts also noted statistical anomalies in the study’s results. “The first question you have to ask is: are the groups well matched — did the authors create two comparable groups whose only difference was COVID-19 vaccine receipt,” Prasad wrote.
Prasad wrote that the study’s authors did not accomplish this.
“In the supplement it is clear they do not achieve adequate matching. All cause mortality curves separate by day 10. That is simply impossibly fast. The MACE [major adverse cardiovascular event] separates by week 5, and the all cause death separates by week 2.”
Mead said this outcome “tells us that the two study arms weren’t comparable from the start. It suggests that those who got the extra COVID booster along with the flu shot were ostensibly healthier, so they had lower MACE and death rates for reasons completely unrelated to the mRNA shots.”
According to immunologist and biochemist Jessica Rose, Ph.D., a potentially “realistic” explanation for this result “is that the ‘no vaccine’ group might have been sicker or frailer from the start” — an indication of a confounding factor, such as healthy vaccinee bias.
“A vaccine shouldn’t rapidly cut deaths from all causes if the groups are balanced. Quick separation screams confounding,” Rose said.
Journal rejects CHD’s rebuttal of the paper
Karl Jablonowski, Ph.D., senior research scientist for Children’s Health Defense (CHD), said the study’s researchers also improperly weighted different subgroups within the “unvaccinated” cohort, skewing the study’s results. He said:
“For most of the comorbidity conditions assessed, the unvaccinated appear healthier than the vaccinated. The unvaccinated have lower incidence (table 1) of COPD, cardiovascular disease, cerebrovascular disease, chronic lung disease, dementia, depression, diabetes, gastrointestinal disease, heart failure, immunocompromised status, myocardial infarction, peripheral artery disease, and stroke.
“For each of those diseases, the unvaccinated cohort is weighted to over-represent the illness and closer match the incidence in the vaccinated. The reweighting spans the unvaccinated demographics as the younger are made to appear older, Blacks are upweighted, whites are underweighted, area deprivation index is underweighted, homelessness is upweighted, etc.”
Jablonowski outlined some of his concerns with the study’s methodology and results in a letter to the editor of JAMA Internal Medicine last week — a copy of which he shared with The Defender.
“This is not a COVID-19 vaccinated vs. unvaccinated comparison in the 2024-2025 season. It is a COVID-19 vaccinated vs. those who chose to suddenly stop COVID-19 vaccination in that season. In upweighting people who suddenly stopped, the authors are underweighting everyone else,” Jablonowski wrote.
According to Jablonowski, when looking at the study’s crude — or unadjusted — results, the data tell a different story. For all-cause MACE, he wrote that the crude vaccine efficacy data show a negative vaccine efficacy (VE) rate of -18.15% among the vaccinated, whereas the weighted VE was 6.2%.
The results were similar for all-cause hospitalization, for which the unweighted vaccine efficacy was -14.3% but the weighted VE was 6.6%. For all-cause death, the crude VE was -11.43% but the weighted VE was 7.1%.
“When such a disparity exists between crude and weighted VE, extra scrutiny is warranted on how the weighting was performed and reported. That extra scrutiny would take the form of sensitivity analyses,” Jablonowski wrote.
The researchers performed 12 different types of sensitivity analyses, but Jablonowski said some of these analyses were improperly done, because the researchers looked at whether members of the “unvaccinated” group had been vaccinated in prior years, then “upweighted” those subgroups to represent a significant part of the “unvaccinated” cohort.
Mead noted that “both study arms were in fact heavily pre-vaccinated,” as “eligibility to be in the study required a 2023-2024 COVID-19 dose.”
“This means that the control, or ‘flu-only,’ arm carried the same history of mRNA vaccine exposure as the booster group, differing mainly in receipt of the 2024-2025 booster formulation,” Mead said.
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‘The headlines are often incorrect’
In his letter, Jablonowski said the study’s authors should repeat their analysis “without including prior immunizations in the inverse probability weighting, coupled with a thorough explanation as to how negative efficacy turned positive.”
However, on Monday, JAMA Internal Medicine’s editor declined to publish Jablonowski’s letter. According to Mead, this is unsurprising.
“JAMA’s decades-long reputation as a mouthpiece for Pharma is once again confirmed — not surprising, given that drug advertising covers as much as 25% of JAMA’s financial overhead,” Mead said.
Dr. Ziyad Al-Aly, director of the Clinical Epidemiology Center at Washington University in St. Louis and one of the study’s co-authors, told the Post that the study “tells us that these vaccines have actually brought beneficial effects even in people who don’t really know that they actually have contracted covid-19.”
But Prasad wrote that mainstream media outlets like the Post lack “in house critical appraisal of science.” As a result, “the headlines are often incorrect.”
The paper “was allowed to pass peer-review to pump out a false narrative, in my opinion,” Rose said.
Related articles in The Defender
- FDA Understated Risk of Heart Damage From Moderna COVID Vaccine, New Study Suggests
- ‘Gravely Concerning’: Spike Protein Found in Female Stroke Victims Up to 17 Months After Receiving mRNA COVID Vaccine
- Study Finds 9.6% Fatality Rate Among People Who Reported Myocarditis or Pericarditis After an mRNA COVID Vaccine
- ‘Stunning’ 620% Higher Risk of Myocarditis After mRNA COVID Vaccines
- Lipid Nanoparticles in COVID Vaccines Travel to Vital Organs, Including Heart
- Watch: Spike Protein Leads to ‘Five Mechanisms of Damage’ in Human Body
