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Vaccines & Autism: Is There A Link?

Medically reviewed on Feb 28, 2017 by L. Anderson, PharmD.

Why Are Vaccines Linked to Autism?

It seems the link between childhood vaccines and of autism is a topic that never fades away. Concerns about vaccines causing autism surfaced in 1999 and initially involved the measles, mumps and rubella (MMR) vaccine. Because the MMR vaccine is usually given at age 12 to 15 months, and the first signs of autism often appear at this time, concerns were raised about a link between the MMR vaccine and the development of autism. In the past, many vaccines given to children contained the preservative thimerosal, as well, and some parents considered thimerosal causative in the development of autism. Preservatives are added to some vaccines to prevent bacterial growth.

What Exactly is Autism, or ASD?

Autism, also known as autism spectrum disorder (ASD), is a brain development disorder in children that leads to problems with communication, behavior, and social interaction. A child may not show signs until age 2 or 3, and symptoms may continue throughout the child’s lifetime.

What exactly causes autism is not known, but most experts agree it is genetically linked. Researchers are also studying whether environmental factors such as viral infections, pregnancy complications, or air pollutants could increase the risk of autism. ASD is 5 times more common in boys than girls; about 1 out of every 68 children are diagnosed with this disorder. There is no known cure for autism, but children can learn new skills.

Medical Experts Weight In

Several studies reported by the U.S. Centers for Disease Control and Prevention (CDC) offer assurance to parents that vaccines do not cause autism. These studies evaluated eight vaccines and also looked at a child's response to antigen development from several vaccines over the first two years of life. Plus, the CDC found that exposure to thimerosal, either early in life or in the womb, does not increase a child’s risk.

Additional studies from Europe, the Institute of Medicine, and the American Academy of Pediatrics have confirmed this; the patient advocacy group Autism Speaks also agrees. Even though the medical evidence strongly supports that vaccines do not cause autism, many parents find the data overwhelming.

What Started This Concern?

A study published in The Lancet in 1998 stated incorrect findings over an association between the MMR vaccine and autism. Since this time, the majority of the authors and The Lancet have retracted the findings. In fact, The Lancet attributed ethical misconduct and inaccuracy on the part of the main author.

In the U.S., many legal cases were brought forth over a supposed link between autism and the MMR vaccine. However, according to the Omnibus Autism Proceeding, it was ruled that the MMR vaccine, either given alone or in conjunction with thimerosal-containing vaccines, was not a causal factor in the development of autism.

Is Thimerosal Still Found in Vaccines?

Thimerosal has been removed or reduced to trace amounts in most vaccines, with the exception of the seasonal flu shot. For parents who prefer, preservative-free versions of the flu shot are available; all you have to do is request it from your doctor or pharmacist.

Thimerosal used to be found in the hepatitis B, Haemophilus influenzae type B (Hib) and diphtheria, tetanus, and pertussis (DTP) vaccines, among others. The U.S. Food and Drug Administration (FDA) has worked with vaccine manufacturers to eliminate thimerosal from vaccines recommended for children 6 years and younger.

Why Are Rates of Autism Going Up?

It is true that rates of diagnosed ASD have risen recently. The Autism and Developmental Disabilities Monitoring (ADDM) Network monitors the prevalence of ASD in the U.S. In 2000, roughly 1 in 150 children were diagnosed with ASD. In 2011, the number had increased to nearly 1 in 68.

However, rates may not be increasing solely because there are more cases of ASD; they might also be increasing due to a broader definition and a better diagnosis of ASD. As the numbers of ASD increase, additional community needs grow too, such as educational services and a coordinated response to families whose children have ASD.

What Are the Most Common Risk Factors for Autism?

Common risk factors for autism include:

  • Having a twin with ASD.
  • Parents who have had a child with ASD have a 2 to 18 percent of having another child with the disorder. Children born to older parents also have a higher risk.
  • About 10% of children with autism are also have certain genetic disorders like Down Syndrome or tuberous sclerosis.
  • Over 80% of children diagnosed with ASD also have a psychiatric, neurologic, chromosomal, or genetic diagnosis.

Diseases and Vaccination in the U.S.

Diseases like polio, whooping cough, measles, Haemophilus influenzae, and diphtheria are becoming very rare in the U.S. because the childhood vaccination programs have worked. If you were to stop vaccinating your child, they would be at risk for these diseases and would put other children and communities at risk, too. The benefit from widespread vaccination protecting the larger community is known as herd immunity.

The more people who are vaccinated, the fewer opportunities a disease has to spread. If vaccination rates drop nationally, diseases could become as common as they were before vaccines. Smallpox is a true success story; it has been eliminated from the globe.

What If I Don't Vaccinate My Child?

It is important to vaccinate to prevent outbreaks of diseases that are nearly under control today. Vaccinations are one of the most important actions we can take to protect ourselves, our children, and our communities from disease. This is especially important for children who cannot be vaccinated because they are too young or sick.

If a case of a disease is introduced into a community where most people are not vaccinated, an outbreak can occur because widespread protection known as "herd immunity" breaks down. In 2013-2014, several measles outbreaks occurred in the U.S. among groups with low vaccination rates, including in the states of Texas, New York and California. Pertussis (whooping cough) has also been on the rise.

Where Can I Learn More About Autism and Vaccines?

The Centers for Disease Control and Prevention (CDC), The American Academy of Pediatrics, and the Food and Drug Administration (FDA) all have information on their websites detailing vaccine use and the risk of autism. Always ask any questions you may have of your pediatrician or other health care provider, too; they will have the latest updates.

Additional Resources

Finished: Vaccines and Autism - Is There A Link?

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  • The U.S. Centers for Disease Control and Prevention (CDC). Vaccines Do Not Cause Autism. Accessed 12/20/2016 at
  • Wakefield, AJ, et al. RETRACTED: Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Accessed 12/20/2016 at
  • Vaccine Refusal a Driving Force Behind Measles Outbreaks, Study Finds. Accessed 12/20/2016 at