Frequently Asked Questions
Q: Do vaccines cause autism spectrum disorder (ASD)?
A: Many studies that have looked at whether there is a relationship between vaccines and autism spectrum disorder (ASD). To date, the studies continue to show that vaccines are not associated with ASD.
However, CDC knows that some parents and others still have concerns. To address these concerns, CDC is part of the Inter-Agency Autism Coordinating Committee (IACC), which is working with the National Vaccine Advisory Committee (NVAC) on this issue. The job of the NVAC is to advise and make recommendations regarding the National Vaccine Program. Communication between the IACC and NVAC will allow each group to share skills and knowledge, improve coordination, and promote better use of research resources on vaccine topics.
For more information about vaccines and ASD, see:
- Mercury and Vaccines (Thimerosal)
- Measles, Mumps, and Rubella (MMR) Vaccines Safety
- Thimerosal in Seasonal Influenza Vaccine
- Timeline: Thimerosal in Vaccines (1999–2010)
- Vaccine Safety: Concerns about Autism
Chart of CDC’s Vaccine and ASD Research [130 KB, 2 Pages, 508]
Q: Is there an ASD epidemic?
A: More people than ever before are being diagnosed with an ASD. It is unclear exactly how much of this increase is due to a broader definition of ASD and better efforts in diagnosis. However, a true increase in the number of people with an ASD cannot be ruled out. We believe the increase in the diagnosis of ASD is likely due to a combination of these factors.
CDC is working with partners to study the prevalence of ASD over time, so that we can find out if the number of children with these disorders is rising, dropping, or staying the same.
We do know that ASD are more common than we thought before and should be considered an important public health concern.
There is still a lot to learn about ASD. In addition, increased concern in the communities, continued demand for services, and reports estimating a prevalence of about 1.7 percent show the need for a coordinated and serious national response to improve the lives of people with ASD.
Learn more about the number of people with ASD »
Q: Can adults be diagnosed with an ASD?
A: Yes, adults can be diagnosed with an ASD. Diagnosis includes looking at the person’s medical history, watching the person’s behavior, and giving the person some psychological tests. But, it can be more challenging to diagnose an adult because it is not always possible to know about the person’s development during the first few years of life, and a long history of other diagnoses may complicate an ASD diagnosis. Because the focus of ASD has been on children, we still have much to learn about the prevalence and causes of ASD across the lifespan. Behavioral interventions can be effective for adults coping with a new diagnosis of autism.
Q: What are mitochondrial diseases or disorders?
A: Mitochondria are tiny parts of almost every cell in your body. Mitochondria are like the power house of the cells. They turn sugar and oxygen into energy that the cells need to work.
In mitochondrial diseases, the mitochondria cannot efficiently turn sugar and oxygen into energy, so the cells do not work correctly.
There are many types of mitochondrial disease, and they can affect different parts of the body: the brain, kidneys, muscles, heart, eyes, ears, and others. Mitochondrial diseases can affect one part of the body or can affect many parts. They can affect those part(s) mildly or very seriously.
Not everyone with a mitochondrial disease will show symptoms. However, when discussing the group of mitochondrial diseases that tend to affect children, symptoms usually appear in the toddler and preschool years.
Mitochondrial diseases and disorders are the same thing.
Q: Is there a relationship between mitochondrial disease and autism?
A: A child with a mitochondrial disease:
- may also have an autism spectrum disorder,
- may have some of the symptoms/signs of autism, or
- may not have any signs or symptoms related to autism.
A child with autism may or may not have a mitochondrial disease. When a child has both autism and a mitochondrial disease, they sometimes have other problems as well, including epilepsy, problems with muscle tone, and/or movement disorders.
More research is needed to find out how common it is for people to have autism and a mitochondrial disorder. Right now, it seems rare. In general, more research about mitochondrial disease and autism is needed.
Q: What is regressive encephalopathy?
A: Encephalopathy is a medical term for a disease or disorder of the brain. It usually means a slowing down of brain function.
Regression happens when a person loses skills that they used to have like walking or talking or even being social.
Regressive encephalopathy means there is a disease or disorder in the brain that makes a person lose skills they once had.
We know that sometimes children with mitochondrial diseases seem to be developing as they should, but around toddler or preschool age, they regress. The disease was there all the time, but something happens that “sets it off”. This could be something like malnutrition, an illness such as flu, a high fever, dehydration, or it could be something else.
Q: Is there a relationship between autism and encephalopathy?
A: Most children with an autism spectrum disorder do not and have not had an encephalopathy. Some children with an autism spectrum disorder have had regression and some have had a regressive encephalopathy.
Q: What do we know about the relationship between mitochondrial disease and other disorders related to the brain?
A: Different parts of the brain have different functions. The area of the brain that is damaged by a mitochondrial disease determines how the person is impacted. This means that a person could have seizures; trouble talking or interacting with people; difficulty eating; muscle weakness, or other problems. They could have one issue or several.
Q: Do vaccines cause or worsen mitochondrial diseases?
A: As of now, there are no scientific studies that say vaccines cause or worsen mitochondrial diseases. We do know that certain illnesses that can be prevented by vaccines, such as the flu, can trigger the regression that is related to a mitochondrial disease. More research is needed to determine if there are rare cases where underlying mitochondrial disorders are triggered by anything related to vaccines. However, we know that for most children, vaccines are a safe and important way to prevent them from getting life-threatening diseases.
Q: Are all children routinely tested for mitochondrial diseases? What about children with autism?
A: Children are not routinely tested for mitochondrial diseases. This includes children with autism and other developmental delays.
Testing is not easy and may involve getting multiple samples of blood, and often samples of muscle. Doctors decide whether testing for mitochondrial diseases should be done based on a child’s signs and symptoms.
Q: Should I have my child tested for a mitochondrial disease?
A: If you are worried that your child might have a mitochondrial disease, talk to your child’s doctor.
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