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Immunizations and autism

Autism is a developmental disorder that some people are born with. You can’t catch it or pass autism along to someone else. It affects the brain and makes communicating and interacting with other people difficult. It begins before a child is three years old. There are a number of different symptoms that may indicate autism. For example, some people with autism often have delayed language development, prefer to spend time alone, and show less interest in making friends.

Some people worry that thimerosal — a compound formerly used in vaccines that is part mercury — can cause autism. Until 1999, vaccines given to infants to protect them against diphtheria, tetanus, pertussis, Haemophilus influenzae type b (Hib), and Hepatitis B contained thimerosal as a preservative. Today, with the exception of some flu vaccines, none of the vaccines used in the U.S. to protect preschool-aged children against 12 infectious diseases contain thimerosal as a preservative. The MMR vaccine does not and never did contain thimerosal. Varicella (chickenpox), inactivated polio (IPV), and pneumococcal conjugate vaccines have also never contained thimerosal.

Many studies have looked to see if there is a link between vaccines and autism. The medical and scientific communities have carefully and thoroughly reviewed the evidence concerning the vaccine-autism theory and have found no association between vaccines and autism. If parents have questions or concerns about childhood vaccines, they should talk with their child’s doctor.

Autism is usually diagnosed at a very young age, between the ages of 1½ and 4 years old. There are no medical tests to determine whether someone has autism, although doctors may run various tests to rule out other causes of the symptoms. Autism does not suddenly begin during the teenage years.

For more information about autism, visit the Centers for Disease Control and Prevention.

Content last updated February 3, 2009

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