Fact or Fiction? Autism
FACT: Vaccines do not cause autism.
It’s a matter of timing.
After an autism diagnosis, parents and caregivers may wonder what caused autism in their child. Children receive the MMR (measles, mumps, and rubella) vaccine around 12 – 15 months. This is the same age when children begin to show diagnosable signs of autism. Because of this timing, caregivers might think the vaccine is connected to their child’s autism diagnosis. But many studies have shown there is no link between autism and vaccines.
People with autism think about and experience the world differently than other people.
These differences can include a person’s social interaction, speech, and behavior. Autism can be a complex diagnosis, but it is a normal part of human diversity.
Over the last 20 years, the rate at which children are diagnosed with autism has increased. However, the criteria for diagnosing autism and access to diagnoses have also expanded. There is broader awareness about autism today than there was in the past. Parents, teachers, and doctors are better able to recognize autism traits and help children get diagnosed. Children who receive an autism diagnosis today may not have received one in the past.
Scientists are still learning what causes autism.
The increase in autism diagnoses has led researchers to explore the causes of autism. Current theories suggest that it is genetic and present starting before birth. For instance, studies of twins found that if one identical twin is diagnosed with autism, it is about 90% likely that their twin will also be diagnosed. Research also suggests that environmental influences during pregnancy can cause autism. Researchers continue to look for other potential contributing factors.
Fortunately, whether vaccines or vaccine ingredients cause autism has been answered by science. The results are clear: vaccines do not cause autism.
One fraudulent study sparked enduring doubt.
Many concerns about a link between vaccines and autism come from a study published by Andrew Wakefield in a research journal called The Lancet. The study included 12 children. It found that the children began to experience the first signs of developmental differences shortly after getting the MMR vaccine. Wakefield was unable to find a clear scientific link between MMR and autism; yet, he concluded that the MMR vaccine should not be used.
In 2010, The Lancet retracted the study. They discovered that Wakefield acted unethically while conducting his research. Wakefield took blood samples from children at his son’s birthday party. Wakefield subjected the children in the study to unnecessary and invasive procedures. He also failed to disclose that he received funding from parents who already had concerns about the MMR vaccine. The British Medical Council found Wakefield guilty on 30 charges of professional misconduct. They took away his medical license and stopped him from practicing medicine.
This fraudulent study has led some caregivers to distrust the MMR vaccine and refuse it for their children. It also ultimately contributed to the resurgence of measles across the world. In the 28 years since the study was first published, there have been nearly 90,000 reported measles cases in England and Wales alone. The U.S. is now experiencing the highest number of measles cases since the disease was considered eradicated in 1991. There were 2,289 reported cases in 2025.
In response to Wakefield’s falsified study, concern over a possible link between vaccines and autism grew. This led researchers to produce dozens of studies across the world looking for any association between vaccines and autism.
None of these studies have been able to recreate Wakefield’s findings or find any connection between the MMR vaccine and autism.
Does thimerosal cause autism?
This is also true for thimerosal. Thimerosal is a preservative that has been used for decades in multi-dose vaccines and medicines to prevent bacterial growth. Thimerosal has not been used in childhood vaccines since 2001. Numerous studies have shown that there is no link between thimerosal and autism.
Does aluminum cause autism?
Aluminum is added to vaccines as an adjuvant. Adjuvants help vaccines produce an effective immune response with a smaller amount of antigen. Aluminum is the third most abundant element on Earth. It occurs naturally in breast milk at 1.5 times the amount in vaccines. Everyday exposure to aluminum is common, and aluminum-adjuvanted vaccines have not been linked to autism.
Does formaldehyde cause autism?
Formaldehyde is used in some vaccines to ensure it does not cause disease. It helps inactivate antigens, like viruses and bacteria, used to make the vaccine. When a baby is born, its body already has 50 times the amount of formaldehyde found in vaccines. Formaldehyde is naturally created by our bodies when our cells make amino acids and DNA. Still, formaldehyde is removed from vaccines after inactivating the antigens. Research confirms that this is completely safe for infants.
After a decade of research, we can confidently say vaccines do not cause autism.
This means that as a parent or caregiver, you can be confident in choosing to immunize your children. It also means that experts can focus on researching autism and providing better support for the autistic community.
Learn more from these additional resources: