I was recently quoted by the New York Times article “Kennedy Says He Told C.D.C. to Change Website’s Language on Autism and Vaccines” published November 21, 2025.
I would like to provide clarity and context for my comments. I do not support the changes that were made to CDC’s vaccines and autism webpage.
Over the past few decades there have been at least 16 rigorous epidemiological studies that have examined the risk of MMR vaccine, thimerosal in vaccines, and multiple vaccines and autism spectrum disorder (ASD) including diphtheria-pertussis-tetanus (DTP) vaccines. None of these 16 studies found a relationship between vaccines and ASD. The Institute for Vaccine Safety has concluded that vaccines do not cause autism – see Do Vaccines Cause Autism?.
In 2004 the Institute of Medicine (IOM) concluded that the body of epidemiological evidence favors rejection of a causal relationship between the MMR vaccine and thimerosal in vaccines and autism. The IOM also stated: “While the committee strongly supports targeted research that focuses on better understanding the disease of autism, from a public health perspective the committee does not consider a significant investment in studies of the theoretical vaccine-autism connection to be useful at this time.” Since this 2004 report, additional studies of vaccines and autism have not shown a relationship and are summarized on our website.
I have long advocated greater federal investment in vaccine safety science. I have promoted the development of a vaccine safety research agenda, a call recently endorsed by the National Academy of Medicine.
It is important for rigorous science to address scientific and public concerns in vaccine safety. However, given limited resources it is essential to focus research on areas that are likely to be impactful.
My position on vaccine safety science and specifically studies around vaccines and autism is well characterized in a recent podcast, with excerpts published in interview format.
Here is the last question from the interview:
What do you think about the idea of doing more research on whether vaccines are linked to autism?
I’m a scientist and I believe in the value of science. The science that has been done has shown that vaccines are very safe. They’re not perfectly safe; they do sometimes, very rarely cause adverse reactions.
But when it comes to autism, the science has already largely been done. If you gave me a pot of money and said, let’s do more vaccine safety research, autism would not be high up on this list because the existing science is already quite compelling.