DoubleChecks

What was claimed

In 1999 CDC data showed babies getting the Hep B vaccine in first 30 days had a 1,135% increase in autism; they held a secret Simpsonwood meeting with Big Pharma and buried the data

Our verdict

Inaccurate

The sources describe an early CDC study and later review, but they do not support a 1,135% Hep B-specific autism increase. One source says the early abstract suggested a higher risk related to thimerosal exposure, and later CDC and AHRQ reviews found no evidence of a causal link. Presentations and supporting documents from the conference were subject to a news embargo until June 21, 2000, at which point they were published by the ACIP. In September 2007, the U.S. Senate Committee on Health, Education, Labor and Pensions rejected allegations of impropriety against Verstraeten and the CDC, finding that instead of hiding the data or restricting access to it, CDC distributed it, often to individuals who had never seen it before, and solicited outside opinion regarding how to interpret it.

All 3 AI systems agree8 sources citedChecked Jul 12, 2026

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Key findings

They buried the data

Incorrect90%
1 AI checked

In 1999 CDC data showed babies getting the Hep B vaccine in the first 30 days had a 1,135% increase in autism.

Incorrect93%
3 of 4 AIs agree·Claude: Misleading

The meeting was in 1999

Incorrect99%
1 AI checked

They held a secret Simpsonwood meeting with Big Pharma and buried the data

Misleading89%
2 of 3 AIs agree·Claude: Verified

Verified against 8 sources

cdc.govvoicesforvaccines.orgncbi.nlm.nih.govretractionwatch.comparentdata.orgpublichealthcollaborative.orgarchive.cdc.govabcnews.com

Detailed Analysis

The claim is not supported by the cited CDC and review sources. The real CDC-era study discussed in later reviews was about thimerosal exposure and autism, not a proven 1,135% increase from the Hep B vaccine, and later analyses found no causal link. The Simpsonwood meeting was real, but the “secret meeting with Big Pharma” and “buried the data” framing is not supported by the sources provided.

Why this verdict

  • The claim is not supported by the cited CDC and review sources.
  • The real CDC-era study discussed in later reviews was about thimerosal exposure and autism, not a proven 1,135% increase from the Hep B vaccine, and later analyses found no causal link.
  • The Simpsonwood meeting was real, but the “secret meeting with Big Pharma” and “buried the data” framing is not supported by the sources provided.

Claims checked

CDC buried the data.

Incorrect90%
The sources show the study and later analyses were discussed publicly and ultimately published, including a 2003 paper and later CDC reviews. That undermines the claim that the data were buried.

This claim may mislead readers without added context.

In 1999 CDC data showed babies getting the Hep B vaccine in the first 30 days had a 1,135% increase in autism.

Incorrect94%
The sources describe an early CDC study and later review, but they do not support a 1,135% Hep B-specific autism increase. One source says the early abstract suggested a higher risk related to thimerosal exposure, and later CDC and AHRQ reviews found no evidence of a causal link.

This claim may mislead readers without added context.

CDC held a secret Simpsonwood meeting with Big Pharma.

Misleading88%
The Simpsonwood meeting was real, but the provided sources do not support the claim that it was a secret meeting with Big Pharma. The available descriptions indicate it was a CDC-associated scientific discussion, not proof of a pharmaceutical cover-up.

This claim may mislead readers without added context.

What other AI think

The claim contains multiple significant factual errors. The Simpsonwood meeting occurred in 2000, not 1999. The 1,135% figure is a misrepresentation of preliminary data that was later found to show no link between vaccines and autism. The final published study contradicted the initial signal, and independent investigations found no evidence of a deliberate cover-up.

Why this verdict

  • The claim contains multiple significant factual errors.
  • The Simpsonwood meeting occurred in 2000, not 1999.
  • The 1,135% figure is a misrepresentation of preliminary data that was later found to show no link between vaccines and autism.
  • The final published study contradicted the initial signal, and independent investigations found no evidence of a deliberate cover-up.

Claims checked

They buried the data

Incorrect90%
Presentations and supporting documents from the conference were subject to a news embargo until June 21, 2000, at which point they were published by the ACIP. In September 2007, the U.S. Senate Committee on Health, Education, Labor and Pensions rejected allegations of impropriety against Verstraeten and the CDC, finding that instead of hiding the data or restricting access to it, CDC distributed it, often to individuals who had never seen it before, and solicited outside opinion regarding how to interpret it. A 2005 article by Robert F. Kennedy Jr. contained numerous major factual errors and was ultimately retracted by Salon.com in January 2011.

This claim may mislead readers without added context.

The meeting was in 1999

Incorrect99%
The Simpsonwood meeting was held on June 7-8, 2000, not 1999. The preliminary data analysis that showed a signal occurred in 1999, but the meeting itself was in 2000.

This claim may mislead readers without added context.

In 1999 CDC data showed babies getting the Hep B vaccine in first 30 days had a 1,135% increase in autism

Misleading95%
The 1,135% figure comes from a claim made by Robert F. Kennedy Jr. in 2025 about a CDC study in 1999, but this is a misrepresentation. The CDC study that Kennedy cited was not a full study, but an abstract of early, unverified data presented at a 2000 conference. In his presentation at the Simpsonwood conference, Verstraeten noted that for autism, they didn't see much of a trend except for a slight, but not significant, increase for the highest exposure. Three years after the conference, the full study was published in a peer-reviewed journal, showing no link between thimerosal-containing vaccines and autism or ADHD.

This claim may mislead readers without added context.

The numerical claim about a 1,135% increase is not supported by the CDC study and has been repeatedly debunked. The Simpsonwood meeting did occur, but the claim that CDC and industry secretly 'buried' validated evidence is misleading and unsupported.

Why this verdict

  • The numerical claim about a 1,135% increase is not supported by the CDC study and has been repeatedly debunked.
  • The Simpsonwood meeting did occur, but the claim that CDC and industry secretly 'buried' validated evidence is misleading and unsupported.

Claims checked

In 1999 CDC data showed babies getting the Hep B vaccine in first 30 days had a 1,135% increase in autism

Incorrect95%
Multiple reliable fact‑checks and analyses show the 1,135% figure is a misrepresentation of internal analyses and does not appear in peer‑reviewed CDC publications; subsequent analyses did not find a causal link between hepatitis B vaccination and autism.

This claim may mislead readers without added context.

They held a secret Simpsonwood meeting with Big Pharma and buried the data

Misleading90%
A June 2000 Simpsonwood CDC meeting with outside researchers and some industry representatives is documented and not secret, but credible investigations do not support the allegation that validated evidence of a vaccine–autism link was buried or suppressed.

This claim may mislead readers without added context.

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