Decades of scientific research have not resulted in an evidence based link between Autism rates and vaccines. Despite this, there are groups of people who continue to claim otherwise. One of those people is Robert F. Kennedy, Jr., and because he is now the Secretary of the U.S Department of Health and Human Services, he has the ability to influence government messaging. If you are confused, you are not alone. Here is what we know.
What Robert F. Kennedy Jr. Claims About Vaccines and Autism
Robert F. Kennedy Jr. has spent years promoting the idea that childhood vaccines, or ingredients in them, can cause autism. The Autism Science Foundation noted as far back as 2017 that he has “continued to publicly promote the discredited theory that vaccines cause autism.” (Autism Science Foundation)
Since becoming U.S. Secretary of Health and Human Services, Mr. Kennedy has gone even further. In November 2025, he ordered a change to the CDC’s “Autism and Vaccines” webpage so that it now states that the claim “vaccines do not cause autism” is not an evidence-based claim and suggests that studies supporting a link have been ignored. (CDC)
Major news outlets and scientific organizations have strongly criticized this change, pointing out that it contradicts decades of research and appears to be driven by politics rather than real scientific evidence. (The Guardian)
Key point: RFK Jr. is asserting that science has not ruled out a link between vaccines and autism. That is his position—but it is at odds with the overwhelming consensus of independent experts worldwide.
What is the basis for Claims About Vaccines and Autism?
There are two basic theories put forth by supporters of the Vaccine/Autism theory:
1. The MMR vaccine causes Autism
This theory finds “support” in a 1998 paper published in The Lancet and authored by a British doctor named Andrew Wakefield. The paper suggested a link between the measles, mumps, and rubella (MMR) vaccine and autism. The basis for the “connection” was the alleged “discovery” by Dr. Wakefield that the onset of autistic symptoms was closely timed with the administration of the MMR vaccine.
However, when the “science” behind the paper was investigated, it was found that Dr. Wakefield had altered or misrepresented the medical histories of all 12 children in the study to make it appear that the autism symptoms appeared shortly after vaccination; even when the actual medical records showed symptoms had begun before the vaccine had ever been given.
Why would Dr. Wakefield do that? Well, it was also discovered that Dr. Wakefield had received over £55,000 in funding from lawyers who were trying to build a legal case against vaccine manufacturers. Investigators also found out that Dr. Wakefield was pursuing a patent for a separate single measles vaccine and a diagnostic test for “autistic enterocolitis,” giving him three potential financial motives for trying to link Autism to the MMR vaccine.
For his efforts, Dr. Wakfield was found guilty by The UK’s General Medical Council of “serious professional misconduct” and showing “callous disregard” for the children involved in his research.
Since then, numerous large-scale epidemiological studies and reviews have been conducted by other researchers; none of which has ever been able to find a link between the MMR vaccine and autism.
2. The thimerosal hypothesis.
Supporters of the Vaccine/Autism link also point to a theory that thimerosal, a mercury-based preservative used in some vaccines (though never in the MMR vaccine), is a “toxin” that causes autism. Thimerosal was removed from most childhood vaccines as a precautionary measure over 20 years ago, despite a lack of evidence linking it to harm, but concerns about it persist within the anti-vaccine movement. Extensive research has found no causal link between thimerosal and autism.
What Major Medical and Scientific Organizations Say
Multiple independent bodies around the world have reviewed the vaccine–autism question repeatedly. Their conclusions are strikingly consistent:
- World Health Organization (WHO) – After reviewing epidemiological and laboratory evidence, WHO’s Global Advisory Committee on Vaccine Safety concluded that existing studies do not show evidence of an association between MMR vaccination and autism. (World Health Organization)
- U.S. National Academies of Sciences (Institute of Medicine) – A major 2004 report concluded that neither the MMR vaccine nor thimerosal-containing vaccines are associated with autism. (National Academies)
- Johns Hopkins Bloomberg School of Public Health – A 2025 article summarizing the evidence states plainly: “Vaccines do not cause autism,” and highlights multiple large studies finding no link between vaccines or their ingredients and autism. (Johns Hopkins Public Health)
- Children’s Hospital of Philadelphia (CHOP) Vaccine Education Center – Reviews the early studies that were used to claim a link and explains why they were deeply flawed or retracted, reaffirming that well-designed studies show no association between MMR or other vaccines and autism. (Children’s Hospital of Philadelphia)
- Autism Speaks & Autism Science Foundation – Autism advocacy groups that are not vaccine manufacturers emphasize that vaccines do not cause autism and have expressed concern that the CDC’s recent wording change could mislead the public. (Autism Speaks)
- National Medical Association (NMA) & Infectious Diseases Society of America (IDSA) – Both have issued 2025 statements stressing that there is no credible scientific evidence that vaccines cause autism and criticizing the CDC’s new language as inconsistent with the data. (National Medical Association)
Big picture: Across governments, universities, and independent medical groups, the scientific conclusion is the same: vaccines have been extensively studied and are not a cause of autism.
What the Large Studies Actually Show
Here are examples of the types of research behind that consensus:
- Massive Danish cohort study (2019)
- Followed over 650,000 children.
- Compared autism rates in vaccinated vs. unvaccinated children, and between children at higher familial risk and those at lower risk.
- Result: No increased risk of autism associated with MMR vaccination. (Annals of Internal Medicine)
- JAMA study of children with autistic siblings (2015)
- Looked specifically at children who had an older sibling with autism (a group at higher baseline risk).
- Result: Getting the MMR vaccine did not increase autism risk, even in these higher-risk families. (Immunize.org)
- Systematic reviews and meta-analyses (2025 review)
- Synthesized results from many studies, including population-based investigations, meta-analyses and mechanistic research.
- Result: Consistently found no causal link between childhood vaccinations (including thimerosal-containing vaccines) and autism spectrum disorder (ASD). (Trends Pediatrics)
- WHO and National Academies reviews
- Evaluated both epidemiological data and proposed biological mechanisms (like mercury or aluminum toxicity).
- Result: Evidence does not support these mechanisms as realistic causes of autism at vaccine exposure levels. (World Health Organization)
What Do the Graphs and Statistics Show?
A. Autism prevalence over time
The CDC’s Autism and Developmental Disabilities Monitoring (ADDM) Network tracks how many 8-year-olds in various U.S. communities are identified with autism:
- In 2000, about 6.7 per 1,000 children (roughly 1 in 150) were identified with autism. (Statista)
- By 2020, this increased to about 27.6 per 1,000 children (roughly 1 in 36). (Statista)
- The latest CDC report for 2022 data shows about 1 in 31 (3.2%) 8-year-old children identified with autism across the ADDM sites. (CDC)
What the graph looks like:
If you plot years on the x-axis (2000–2022) and autism prevalence per 1,000 children on the y-axis, you get an upward-sloping line—prevalence rising from about 6.7 to around 32 per 1,000. That’s the trend you’ll see in CDC and Statista charts that visualize these data. (CDC)
Researchers attribute this rise mostly to:
- Broader diagnostic criteria
- Greater awareness among parents and clinicians
- Better early screening and services
B. Vaccine coverage over the same period
Over those same decades:
- Coverage with key childhood vaccines like MMR in the U.S. has stayed high and relatively stable, not rising in a way that tracks the increases in autism diagnoses. (Immunize.org)
If you overlay two lines on one graph:
- Line 1: Autism prevalence (rising sharply).
- Line 2: MMR vaccination coverage (mostly flat, high 90% range in many communities).
You do not see the kind of matching pattern you’d expect if MMR were a driving cause of autism diagnoses.
C. The thimerosal natural experiment
Thimerosal is a mercury-containing preservative that was removed from or reduced to trace levels in routine childhood vaccines in the U.S. starting around 1999–2001.
- If thimerosal were a major cause of autism, you’d expect autism diagnoses to fall after its removal.
- Instead, autism prevalence continued to rise in the years after thimerosal was phased out. (National Academies)
Graphically, if you mark the period when thimerosal was removed and then plot autism prevalence over time, the line does not slope downward—it keeps climbing. That pattern strongly argues against thimerosal in vaccines as a cause.
Are Any Specific Vaccines or Ingredients Linked to Autism?
Based on the bodies of evidence reviewed:
- MMR vaccine: No association with autism in large cohort and case-control studies across several countries. (World Health Organization)
- Thimerosal (mercury-based preservative): National Academies and other reviews find no association between thimerosal-containing vaccines and autism. (National Academies)
- Aluminum adjuvants: A recent Danish study RFK Jr. criticized found no link between aluminum in vaccines and neurodevelopmental disorders; he even called for it to be retracted, but the journal refused because the data did not support his claims. (Nature)
At this point, no specific vaccine or vaccine ingredient has been credibly shown to cause autism in humans at the doses used in immunization schedules.
Why the Myth Persists
Even though the data are clear, the idea that vaccines cause autism persists for several reasons:
- Timing: Many autism signs appear between 1–3 years of age—exactly when children get several vaccines. That makes it easy to confuse correlation (two things happening around the same time) with causation. Autism organizations note that this is a coincidence, not a cause. (Autism Speaks)
- A powerful but fraudulent origin story: The 1998 Andrew Wakefield paper that first triggered the MMR–autism scare was later exposed as deeply flawed and unethical, and it was fully retracted. (PMC)
- Misinformation amplification: Social media, blogs, and some advocacy groups amplify anecdotal stories while dismissing large, carefully conducted studies.
- Distrust of institutions: When public agencies change messaging for political reasons—as appears to have happened with the CDC’s recent website change—it can fuel confusion and mistrust, even though the underlying science has not changed. (KFF)
How to approach this question for yourself or your family
- Look for consensus, not isolated voices. When organizations as diverse as WHO, the National Academies, Autism Speaks, and major medical societies all converge on the same conclusion, that’s a strong signal. (World Health Organization)
- Prioritize large, well-designed studies over anecdotal reports. Stories matter emotionally, but they don’t tell you what is statistically true across millions of children.
- Talk with a trusted healthcare professional. A pediatrician or developmental specialist can help you weigh benefits and risks for your child’s specific situation and answer detailed questions about ingredients, schedules, and alternatives.
Bottom Line
- Robert F. Kennedy Jr. continues to claim that vaccines may cause autism and has recently pushed the CDC to alter its website language in that direction, despite the absence of new supporting evidence. (Reuters)
- The scientific evidence, built over decades and involving millions of children, does not support a causal link between vaccines (including MMR and thimerosal-containing vaccines) and autism. (Trends Pediatrics)
- Graphs of autism prevalence and vaccine coverage show rising autism diagnoses over time while vaccination rates remain high and relatively stable, and autism continues to rise even after suspected ingredients like thimerosal were removed—patterns that do not match what you would expect if vaccines were a cause. (CDC)
If you’re worried or unsure, it’s entirely reasonable to ask questions. The most helpful thing you can do is bring those questions to a clinician who understands both autism and vaccines, and rely on evidence from independent medical and scientific organizations rather than politically influenced messaging.