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2019 report by TV host Sharyl Attkisson exaggerates one expert’s opinion in court case to claim vaccines cause autism

Government silenced “top expert witness” who denied the vaccine-autism link in court and changed opinion; his testimony could have changed the court’s decision
Inaccurate: Research shows that vaccines don’t cause autism. A link between vaccination and autism in children with genetic mitochondrial disorders is also unsupported by scientific evidence.
Misleading: A U.S. court’s decision to reject thousands of claims arguing that vaccines caused autism was based on the testimony of numerous experts. Pediatrician Andrew Zimmerman was only one of them. His later affidavit suggesting that vaccines could cause autism in children with mitochondrial diseases, in itself, would have been unlikely to alter the court’s decision.
The Omnibus Autism Proceeding was a legal process that aimed to collectively resolve thousands of vaccine injury claims submitted to the National Childhood Vaccine Injury Compensation Program in the late 1990s. The petitions were based on incorrect allegations that vaccines caused autism in children. The U.S. Court of Federal Claims ultimately rejected all the petitions after finding no evidence supporting the claims. Multiple large studies have shown that vaccines don’t cause autism.

FULL CLAIM: “Top expert witness” who denied the vaccine-autism link in court changed opinion proving that “vaccines can cause autism after all” but government officials “kept it secret”; “That turnabout [...] stood to change everything about the vaccine-autism debate if the public were to find out”


On 6 January 2019, an episode of the TV show Full Measure, hosted by journalist Sharyl Attkisson, went viral on social media. The episode, titled “The Vaccine Debate”, claimed to provide evidence that the U.S. government knew long ago that vaccines could cause autism but hid this information from the public. The episode also implied that this hidden information could have changed a court’s decision to reject thousands of injury claims alleging that vaccination had caused autism in children.

A segment of “The Vaccine Debate” with the caption “AUTISM. THEY KNEW!” circulated again on social media in March 2024. One Instagram reel sharing this segment received more than 150,000 views.

Attkisson has propagated vaccine misinformation multiple times in the past. Her antivaccine messages date back to as early as 2007, when she authored an article for CBS News falsely linking childhood vaccination and autism. Attkisson has since repeated this claim on multiple occasions.

However, this claim is contradicted by scientific evidence. Numerous studies demonstrate that vaccines are safe, prevent dangerous infections, and don’t cause autism[1-4]. “The Vaccine Debate” doesn’t show otherwise and contains several misleading claims, which we will review below.

What is the context surrounding Attkisson’s vaccine-autism claim?

Attkisson’s claim is related to the Omnibus Autism Proceeding, a special legal process established by the U.S. National Childhood Vaccine Injury Compensation Program (VICP) in 2002. This proceeding aimed to jointly resolve roughly 5,000 injury claims submitted to the VICP in previous years. To do that, it used a set of six “test cases” to determine whether autism was causally associated with childhood vaccines.

The “test cases” were selected by the petitioner’s attorneys from all the submitted claims as the best evidence for the vaccine-autism link. The decision on these “test cases” was intended to apply to the remaining individual cases.

It’s important to stress that scientific evidence has shown no link between vaccines and autism. However, the VICP is a no-fault system. This means that even when a causal effect cannot be proven, petitioners may still receive compensation if they offer a plausible biological mechanism explaining how the vaccine might cause the health problem. Evidence of plausibility is usually provided through the testimony of expert witnesses, who present the scientific evidence supporting or rejecting a causal link. After hearing expert opinions from both parties, the court then decides whether the proposed mechanism has sufficient scientific support.

Thus, each test case argued that there was a causal relationship between vaccination and autism through three proposed mechanisms: 1) the mercury-containing compound thimerosal, 2) the measles, mumps, and rubella (MMR) vaccine, or 3) the combination of both.

The Office of Special Masters of the U.S. Court of Federal Claims, which manages vaccine litigations, held hearings on the six cases and announced its decisions in 2009 and 2010. The petitioners’ claims were all rejected after the Office found no evidence of a causal relationship between thimerosal or MMR vaccines and autism.

The “top expert” Attkisson referenced was just one out of multiple experts consulted during the proceedings

The “top expert witness” that Attkisson referred to in the Full Measure report is Andrew Zimmermann, a pediatric neurologist who provided expert opinion for the Secretary of Health and Human Services, the defendant in the Omnibus Autism Proceeding.

Attkisson alleged that the court’s decision to reject the petitioners’ claims “was based largely” on Zimmerman’s testimony. She added that, during the proceeding, Zimmerman tried to amend his testimony to include one instance in which vaccines could cause autism, but the government hid this evidence. Finally, Attkisson further implied that the court’s decision on the Omnibus Autism Proceeding would have been different had Zimmerman’s amendment been included.

In June 2007, Zimmerman testified in a written statement on one of the six “test cases” (Cedillo v. Secretary of Health and Human Services). The petitioners in this case alleged that thimerosal-containing vaccines damaged the immune system of a toddler named Michelle Cedillo. They claimed that this allowed the weakened measles virus in the MMR vaccine to cause a persistent infection leading to autism.

In his testimony, Zimmerman stated that “the evidence does not support the proposition” that the combined effect of thimerosal and the MMR vaccine had caused Cedillo’s autism.

Zimmerman’s statement supported the decision of the special master, an official appointed by the judge who manages and adjudicates vaccine claims. The special master for the Cedillo case concluded that it was “extremely unlikely that any of Michelle’s disorders were in any way causally connected to her MMR vaccination, or any other vaccination”. He added, “[t]he overall weight of the evidence is overwhelmingly contrary to the petitioners’ causation theories”.

In October 2007, Zimmerman’s statement was cited as evidence in another test case, Hazlehurst v. Secretary of Health and Human Services. In this case, the parents of William Yates Hazlehurst filed a petition claiming that the MMR vaccine had caused their son’s autism. The special master for the Hazlehurst case concluded that “the combination of the thimerosal-containing vaccines and the MMR vaccine are not causal factors in the development of autism and therefore, could not have contributed to the development of Yates’ autism”.

But in September 2018, Zimmerman wrote an affidavit (published in full by Attkisson) stating that using his original written expert opinion as evidence in the Hazlehurst case had been “highly misleading” because it applied specifically to Cedillo’s case.

According to Zimmerman, “vaccine induced fever and immunological stimulation” in children with an underlying mitochondrial disease could potentially cause autism symptoms compatible with Hazlehurst’s case. Zimmerman added that he was supposed to testify orally in Cedillo’s case. However, shortly after trying to amend his original statement to include this exception, he was informed he “would no longer be needed as an expert witness”.

Attkisson argued that Zimmerman was a principal expert witness, and thus including his amendment and allowing him to testify orally would have changed the court’s decision on Hazlehurst’s case—and by extension on the thousands of individual cases relying on it. However, this claim is misleading and unsupported.

First, it’s false to claim that the court’s decision “was largely based” on Zimmerman’s testimony. As the decision documents show, petitioners and defendants appointed six and nine expert witnesses respectively to testify orally for Cedillo’s case. In Hazlehurst’s case, petitioners and defendants presented oral evidence from seven and fourteen experts respectively. In addition, the Secretary of Health and Human Services submitted written reports from three additional experts for Cedillo’s case and four for Hazlehurst’s case. Zimmerman’s was one of them.

All the testimonies presented by the defendants supported the court’s decision. The special master in Cedillo’s case concluded that the experts appointed by the defense “were far better qualified, far more experienced, and far more persuasive than the petitioners’ experts” and the evidence had “come down strongly against the petitioners’ contentions”.

This shows that Zimmerman wasn’t the key expert Attkisson portrayed but simply one of many experts whose testimony contributed to the court’s decision to reject the petitioner’s claims.

Second, even if Zimmerman was indeed asked not to testify orally, he was appointed to Cedillo’s case, not Hazlehurst’s. The special master who handled Hazlehursts’ case stated that his decision relied “more heavily on the testimony and reports of the experts who were observed and heard during the hearings”. Therefore, contrary to Attkisson’s claim, an amendment in Zimmerman’s testimony wouldn’t have had much weight in the court’s final decision.

Finally, in response to Attkisson’s report, Zimmerman issued a press release through the University of Massachusetts Medical School, saying his affidavit had been “misrepresented”. In the press release, Zimmerman highlighted “the importance of vaccines as the best way to prevent many serious diseases”, although he also reiterated some of the statements he made in the 2018 affidavit. Notably, Zimmerman acknowledged that his affidavit was written at the request of Yates Hazlehurst’s father and Robert F. Kennedy Jr., the founder of the antivaccine organization Children’s Health Defense.

Scientific studies don’t support a link between vaccines and autism in children with genetic mitochondrial disorders

Attkisson’s report sent the highly misleading message that Zimmerman’s alleged attempt to amend his testimony demonstrates “vaccines can cause autism after all”.

Several experts, including members of the Mitochondrial Medicine Society, told Science Feedback in an earlier review that the belief that vaccination might trigger autism in children with genetic mitochondrial disorders is unsupported by scientific evidence.

Claims linking vaccines, mitochondrial diseases, and autism originate from the 2006 case report of Hannah Poling, which Zimmerman co-authored. A few days after receiving her scheduled vaccinations, 19-month-old Hannah developed a fever and rash consistent with vaccine-induced varicella. Some months later, she was diagnosed with encephalopathy and developmental regression with clinical features of autism caused by a mitochondrial enzyme deficiency. The family associated this diagnosis with the side effects of vaccination.

There are no scientific studies so far indicating that vaccines cause or worsen mitochondrial diseases. The regressive encephalopathy that affected Poling is a known complication of mitochondrial diseases caused by a congenital brain defect. However, factors such as infections, high fever, malnutrition, or dehydration can trigger the so-called “regression”, which can cause a person to lose skills like walking or talking.

In a commentary for The New England Journal of Medicine, pediatrician Paul Offit explained that fever is more commonly associated with infections, to which children with mitochondrial disorders are more susceptible. For this reason, vaccination is particularly important in these children, as it minimizes the risk of severe infections and complications, including regressive encephalopathy[5]. Offit also noted that Hannah had frequent episodes of fever and ear infections, which might have acted as triggers for the regression.

In short, Zimmerman’s argument that vaccination might trigger autistic symptoms in children with mitochondrial disorders is unsupported by scientific evidence. Given that no scientific studies so far support this hypothesis, it is unlikely that Zimmerman’s testimony would have provided sufficient evidence to produce a change in the court’s decision.

Notably, Zimmerman’s testimony in later similar cases was questioned by the Court. In a 2012 case, for example, the special master rejected the petitioner’s claim, stating that Zimmerman’s opinion was anecdotal. Zimmerman’s statements for this case are publicly available, contradicting Attkisson’s narrative that such opinions are being “silenced”.


Attkisson’s report is misleading and exaggerates the weight of Zimmerman’s expert opinion during the Omnibus Autism Proceeding. This legal process included testimonies from many other experts who spoke about the lack of evidence for a link between vaccines and autism.

It is therefore doubtful that a change in Zimmerman’s opinion alone would have altered the court’s final decision. Moreover, Zimmerman’s claim that vaccination can exacerbate preexisting genetic mitochondrial disorders and result in autism is unsupported by scientific evidence. Scientific evidence shows that vaccines don’t cause autism.



Published on: 03 Apr 2024 | Editor:

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