Receiving a life-altering diagnosis for a child is overwhelming, prompting a deep search for understanding and the reasons behind it. This can be especially true when the condition is as significant and complex as autism spectrum disorder.
With autism, there is a lot we know, there are places we need to study more and there are answers we already have: vaccines and their ingredients are not the cause.
Decades of scientific research and peer-reviewed studies have found no connection exists between vaccines or their ingredients and autism. While researchers continue to study its underlying causes, increases in autism diagnoses are better explained by expanded diagnostic criteria, improved screening and greater public awareness – not vaccines.
Here are three key things to know:
- The evidence is clear. Decades of data show that vaccines and their ingredients do not cause autism.
- Vaccines save lives. The benefits of childhood vaccination far outweigh any potential risks. Vaccines protect children from dangerous diseases that can cause severe illness, long-term complications, cancer and even death.
- False claims have real costs. Revisiting questions that have been asked and answered many times over diverts resources from promising research and progress.
Go deeper: Vaccines are one of the most effective tools we have to keep children and families protected from serious diseases. More than 50 years of clinical studies and real-world use show that the benefits of routine childhood vaccines far outweigh any potential risks. Further, vaccines are closely monitored for safety after approval by government agencies, manufacturers, universities and health systems across the country.
It is critical that conversations are grounded in scientific evidence: vaccines protect against disease, and there is no credible scientific evidence connecting them to autism.
A closer look at the facts:
Thimerosal and aluminum ingredients
Thimerosal is a preservative that has been used in some vaccines to prevent bacterial or fungal contamination. Numerous large-scale studies and reviews spanning more than 20 years have repeatedly confirmed there is no link between vaccines containing thimerosal and autism or other long-term health issues. Since 2001, all vaccines routinely recommended for children six years of age and younger are available in thimerosal-free formulations.
Aluminum is used in vaccines in miniscule amounts – far less than what people encounter through their diet or the environment – to help boost the body’s immune response, making vaccines more effective at a smaller dose. Moreover, a publicly funded, peer-reviewed study in 2025 found no connection between cumulative aluminum exposure from vaccines in early childhood and 50 chronic conditions, including autoimmune diseases, allergies and neurodevelopmental disorders like autism and ADHD.
The MMR (Measles, mumps, rubella) vaccine
Measles was declared eliminated in the United States in 2000, thanks to widespread vaccination with the MMR vaccine. Rigorous testing and decades of real-world data and research – including a 2019 study of over 650,000 Danish children – found no evidence of a connection between autism and MMR vaccines.
Childhood vaccine schedule
Extensive evidence from multiple large-scale studies, including a meta-analysis of millions of children, found no link between the recommended childhood vaccine schedule and autism.
Hepatitis B vaccines
Hepatitis B is called a “silent epidemic” because most people do not have symptoms when they are newly infected or chronically infected. Thus, they can unknowingly spread the virus to others and continue the silent spread of hepatitis B. When infants become infected with hepatitis B, they have about a 90% chance of developing a lifelong, chronic infection. Complications from the infection are much more likely if they get infected in the early days of their lives.
The bottom line: Claims attempting to link vaccines to autism have been thoroughly and consistently debunked by a vast body of scientific research. Vaccines are critical tools that protect our country from dangerous disease and strengthen our nation’s public health – and we must ensure we have a robust vaccine infrastructure that reinforces their value to people and society as a whole.
Read PhRMA’s statement on autism from September 22, 2025.
Mike Ybarra
Michael Ybarra, M.D., is an emergency physician and Chief Medical Officer at PhRMA. He also serves as Senior Vice President in Advocacy and Strategic Alliances. In these roles, he leads PhRMA’s stakeholder engagement and strategic partnerships on federal and international health policy issues. He is PhRMA’s liaison representative to the Advisory Committee on Immunization Practices and is the co-convener of PhRMA’s R&D Leadership Forum. Dr. Ybarra continues to see patients clinically in the emergency department at MedStar Georgetown University Hospital.
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Mike Ybarra