Whopper of the Week: Kennedy claims that vaccines cause autism

This week's Whopper: 

Robert F. Kennedy Jr.'s repeated claims that vaccines cause autism

In summary:

In April 2025, Kennedy claimed, “In September, we will know  what has caused the autism epidemic and we’ll be able to eliminate those exposures". He has repeated numerous times over the past two decades the falsehood that vaccines are the cause of autism spectrum disorder (ASD). This has prompted serious concerns that he will fabricate data to make it appear that there is support for these false claims in his upcoming report. The question of whether vaccines, especially Measles Mumps and Rubella (MMR) vaccine, cause ASD has been asked, answered, and resolved to the satisfaction of scientists and healthcare workers. Vaccines do not cause autism.

Why is this a Whopper?

A detailed explanation of how we know that vaccines do not cause ASD can be found in Defend Public Health's report on what is known about risk factors for ASD. In short, studies with data from millions of children have shown that there is no relationship between vaccines or their ingredients and ASD. The ingredient thimerosal was studied with data from every child born in Denmark from 1971-2000 and the results showed that rates of ASD did not drop after thimerosal was removed from vaccines. The same is true for the United States, where thimerosal was removed from all childhood vaccines in 2001. 

Another vaccine ingredient that has been targeted by misinformation is aluminum, tiny amounts of which are sometimes included in vaccines to help the body mount a more robust immune response. Research with data from more than a million children born between 1997 and 2020 showed that none of the 50 disorders studied, including ASD, showed any relationship to the amount of aluminum exposure from vaccines. Mr. Kennedy demanded that this paper be retracted, based not on science but because he doesn’t like the results. Annals of Internal Medicine, a very prestigious medical journal, correctly refused to do so. 

Large studies have also investigated whether rates of ASD are higher among those who are vaccinated compared to those who are unvaccinated, and have found that they are not.

How might this impact you?

The impacts of the continued spread of misinformation about vaccines causing ASD may impact you in several ways. First, it can endanger children by discouraging vaccination. Sowing doubt about vaccine safety, as Kennedy has done for decades, reduces uptake of vaccines and increases the risk of outbreaks. If Kennedy includes false information in the report, it could potentially be used to modify the childhood immunization schedule and restrict access to vaccines, undermining herd immunity and putting the country and the world at risk for outbreaks of vaccine-preventable diseases. The repeated misinformation from Kennedy about ASD in general leads to greater stigmatization of this condition.

As stated by the Autism Science Foundation:

"Families and individuals affected by ASD deserve scientifically sound and evidence-based information about the causes of ASD, early detection and diagnosis, intervention opportunities, services, and supports. Families and individuals with autism should have direct access to the best scientific information".

Contributors to this post are: Benedicte Callan, PhD; Aurora Horstcamp, MD; and Miriam Rabkin, MD, MPH.