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Testimony by Steve Kirsch on the alleged harms of vaccination relies on flawed, biased analyses

Posted on:  2023-08-10

Key takeaway

Childhood vaccination represents a great advancement in public health that has helped to eliminate or reduce the risk of diseases that in the past killed and disabled more than two million children worldwide per year. A robust body of evidence shows that the vaccines that are currently in use, including COVID-19 vaccines, are safe for children and not associated with a higher risk of adverse health outcomes.

Reviewed content


“All these vaccines are causing harm to our kids”; “The fully unvaccinated kids are always healthier”; “vaccines are causing chronic disease in America”

Source: Twitter, Steve Kirsch, 2023-06-09

Verdict detail

Factually inaccurate: Well-conducted studies show that childhood vaccination prevents potentially serious infections and isn’t associated with poorer health or a higher risk of chronic conditions. COVID-19 vaccines have also demonstrated their safety and efficacy against severe COVID-19, which helped prevent millions of deaths worldwide.
Inadequate support: The two studies that Kirsch cited in his testimony have significant methodological issues that led to the retraction of one of them. The other reference is a flawed, biased report conducted by anti-vaccine groups, which renders its findings unreliable.

Full Claim

“All these vaccines are causing harm to our kids. It’s not just the COVID vaccines; it’s every single one of them”; “The fully unvaccinated kids are always healthier”; “vaccines are causing chronic disease in America”


Vaccines protect against potentially life-threatening infectious diseases. Thanks to vaccination, some infections, like smallpox and polio, that took more than 400 million lives globally and disabled many others are now eradicated or significantly reduced. Thus, vaccines prevent an estimated three to five million deaths per year and are considered one of the greatest achievements in public health[1].

Despite this success, claims that vaccines cause more harm than the diseases they prevent have been persistent. Such narratives fuel vaccine hesitancy[2] and have contributed to a decline in vaccine coverage exacerbated by the COVID-19 pandemic that threatens to set back the progress made against vaccine-preventable diseases over the past thirty years.

One example is this video in which entrepreneur Steve Kirsch—who has repeatedly made false claims about vaccines—claimed that vaccines harm children and “are causing chronic disease in America”, and that “The fully unvaccinated kids are always healthier”. He added, “It’s not just the COVID vaccines; it’s every single one of them”.

Kirsch’s video is an excerpt from his testimony in front of the “Medical Freedom Panel 2023” at the Pennsylvania State Senate on 9 June 2023. The excerpt went viral on social media platforms in early August 2023 (examples here and here), many of the copies originating from a tweet from an anonymous account called The Vigilant Fox that has previously spread misinformation. At the time of this review’s publication, this tweet alone accumulated over two million views and 13,000 retweets.

In his testimony, Kirsch cited two references to back his claims that vaccines are harmful. However, one of them has been retracted because its conclusions were unsupported by the data presented. The other is riddled with potential biases and methodological flaws that make its conclusions unreliable, as this review will show below. Therefore, these results don’t change the evidence from robust studies showing that vaccination isn’t associated with poorer health outcomes.

A now-retracted study by Lyons-Weiler and Thomas used an unvalidated metric to assess disease burden in vaccinated and unvaccinated children

Kirsch’s first reference is a study by bioinformatician James Lyons-Weiler and pediatrician Paul Thomas supposedly showing that fully unvaccinated children are healthier than vaccinated children. The study was published in the International Journal of Environmental Research in November 2020. However, it was retracted by the journal in July 2021 because “the conclusions were not supported by strong scientific data”.

The study’s authors, Lyons-Weiler and Thomas, have been promoting vaccine misinformation for years. In fact, the Oregon Medical Board suspended Thomas’ medical license in December 2020 after concluding that his continued practice placed his patients “at serious risk of harm”. Among other issues, the Board found that Thomas promoted an alternative vaccine schedule that delayed vaccinations, unnecessarily exposing children to preventable infections. MedPageToday reported in July 2021 that the Board permitted Thomas to practice while investigations continued, on the condition that he should not “engage in any discussions with patients or families about vaccine protocols nor conduct research involving patient care”.

The study’s retraction didn’t stop anti-vaccine circles from continuing to cite it as supporting evidence that vaccines are unnecessary or even harmful, as Health Feedback documented in an earlier review. Kirsch’s testimony is yet another example.

Briefly, the study aimed to evaluate differences in disease burden between unvaccinated and vaccinated children. To do that, the authors compared the total number of billing and medical records of 3,324 patients—561 fully unvaccinated and 2,763 who had received at least one vaccine—at a clinic run by Thomas. The authors called this number “Relative Incidence of Office Visits” (RIOV).

Based on this metric, the authors concluded that the fully unvaccinated children had fewer medical conditions compared to the vaccinated group and were, therefore, healthier. But as cancer surgeon David Gorski highlighted in this article, the RIOV is an unvalidated metric, and the authors failed to demonstrate that this metric accurately reflects disease burden.

Furthermore, Thomas’ belief that vaccines cause autism introduces a potential bias in his diagnoses that could also alter the RIOV, making it unreliable even if it were a valid metric, as Gorski also pointed out. For example, vaccinated children might be more likely to be tested for and diagnosed with certain conditions like autism compared to unvaccinated children.

In other words, the results from the study by Lyons-Weiler and Thomas are unreliable owing to potential bias and the use of an unvalidated method for measuring disease burden.

What is the “Control Group study”?

The second reference that Kirsch cited was an alleged study conducted by the Control Group Cooperative (CGC). According to its website vaxcontrolgroup.com, the group was created in 2021 with the objective of recording “long-term health outcomes” in people who didn’t receive a COVID-19 vaccine.

Thus, the CGC encouraged unvaccinated people to register and introduce their personal and health data on the platform. Participants were also requested to complete a monthly online survey with questions about their health, wellbeing, and use of supplements within the previous month.

The website showed one single publication based on these data, a report by Verkerk et al. that is most likely the study Kirsch referred to in his testimony.

The report was initially uploaded as a preprint on the scientific social network ResearchGate in June 2022. However, the platform removed it within a day, alleging that it breached the platform’s terms and conditions. In August 2022, the report was published in the International Journal of Vaccine Theory, Practice, and Research, a journal that often publishes vaccine misinformation, as documented in two articles by Retraction Watch and Gorski.

Verkerk et al. evaluated health outcomes, including COVID-19 cases and hospitalizations, in a subset of 18,497 unvaccinated people from all over the world who completed the CGC survey between 2021 and 2022. After comparing these data with national data from the U.S. Centers for Disease Control and Prevention, the authors concluded that the rate of COVID-19 hospitalization was lower and the disease less severe among the unvaccinated population compared to the general and mostly vaccinated population.

The report by the Control Group is biased, promoted by anti-vaccine groups

Surveys need to be very carefully designed in order to collect the most accurate responses from participants and minimize potential biases[3]. And in this regard, the report by Verkerk et al. is far from reassuring.

For starters, self-reports can be prone to exaggeration or confirmation bias. This is a type of bias in which the person (the researcher or the participant) tends to retrieve information that confirms their pre-existing ideas or beliefs while disregarding the evidence contradicting those ideas. Considering that the CGC data collection targeted participants who refused COVID-19 vaccination, the risk of confirmation bias in their responses is likely quite high.

Correcting for this bias requires that the researchers independently verify responses with other data, such as the participants’ medical records. There is no indication that the CGC did so, at least not consistently.

The issue of potential bias is further reinforced by the fact that the first author of the analysis is Robert Verkerk, founder of the Alliance for Natural Health. Media Bias/Fact Check rates this organization as “a Strong Conspiracy and Pseudoscience organization based on the promotion of anti-Vaccine propaganda and not aligning with the consensus of science”.

The Alliance for Natural Health is only one of the several anti-vaccine affiliates of the CGC, which also include the World Council for Health, Unjected, and Health Freedom Ireland, a group founded by biologist and misinformation spreader Dolores Cahill.

The involvement of all these players might explain the extensive use of anti-vaccine language in the report. This included falsely referring to COVID-19 vaccines as an “experiment” (abstract, page 1) and incorrectly suggesting that the vaccines cause shedding to which unvaccinated people can be “exposed” (questionnaire, page 31).

It is also striking that the CGC offered to those who registered a digital ID card stating that, as participants of a “vaccine study” they “must not be vaccinated”. The report by Verkerk et al. highlighted how this card had been “successful in preventing forced vaccination”. In fact, the website encouraged participants to use this ID as a vaccine exemption card when traveling or accessing events.

Some participants apparently did so, given a Twitter thread by the Government of Manitoba, Canada, which warned in December 2021 about the use of these false vaccine exemption cards in the region and referred to the CGC study as a potential scam.

The report by Verkerk et al. promoted supplements and unproven therapies

Verkerk et al. suggested that “self-care” with specific supplements and “treatments” in the unvaccinated CGC cohort might have contributed to the alleged better COVID-19 outcomes in this population compared to the general population.

Specifically, the authors mentioned vitamin C, vitamin D, zinc, quercetin, and the antiparasitic drugs ivermectin and hydroxychloroquine, none of which have proven effective at preventing or treating COVID-19.

It is worth mentioning that the CGC website sells some of these products, including vitamins, minerals, and essential oils, offering discounts to those who registered. While registering on the platform is free, participants are encouraged to become members for a monthly subscription fee. Some CGC affiliates also promoted unproven COVID-19 therapies and protocols to supposedly “detox” from vaccination. Experts have stated that COVID-19 vaccines aren’t “toxic” and it is not possible nor necessary to detox from vaccination.

Overall, this raises serious concerns about the true nature and objectivity of the report and the CGC collection itself, which together with the multiple methodological issues and signs of bias, render the results of the report unreliable. Therefore, neither of the studies cited by Kirsch actually provides reliable evidence for his claims that vaccines harm children and cause chronic conditions.

In another excerpt from the same testimony that circulated in July 2023, Kirsch made a similar claim without providing any supporting evidence. He said the Amish communities don’t have chronic diseases because they are unvaccinated. Health Feedback addressed this claim in an earlier review and found both statements to be inaccurate.

A large body of evidence shows that vaccines are safe and don’t increase the risk of poorer health

Research and extensive monitoring continue to confirm that vaccines are safe and protect against potentially life-threatening infections. Before receiving approval from regulatory agencies, all vaccines must demonstrate their safety and efficacy through several stages of clinical trials. Then, a panel of medical and public health experts reviews these data in the context of the existing immunization schedule in each country to issue a recommendation.

Well-conducted studies, much more reliable than the ones cited by Kirsch, show that COVID-19 vaccines are safe for children[4], and likely prevented millions of deaths worldwide[5]. Although certain COVID-19 vaccines have been associated with rare cases of heart inflammation and blood clotting, such cases are very infrequent and the vast majority of people only experience mild, transient side effects.

Kirsch’s claim that vaccination leads to chronic diseases is also unsubstantiated and contradicted by scientific evidence, as Health Feedback explained in earlier reviews. Robust studies found no association between vaccines or their ingredients with poorer health or with conditions such as asthma, infections, autoimmune diseases, cognitive delay, autism spectrum disorder, and attention deficit/hyperactive disorder, among others[6-12].

On the contrary, by protecting against serious illnesses, vaccines have contributed to improving global health.


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