Topic Overview

There has been ongoing controversy surrounding certain vaccines and their relationship to autism. Some parents have been concerned that vaccines, specifically the measles-mumps-rubella (MMR) vaccine and preservatives used in other childhood vaccines, play a role in children developing autism. There have been a lot of false claims in the news. But thorough studies have found no link between vaccines and autism.^{footnote 1} A lot of research has been and is being done to find out the cause of autism. Go to www.cdc.gov/ncbddd/autism/seed.html to follow a very large U.S. study about the risks for autism and other developmental disabilities.

Because the exact cause of this sometimes devastating condition is not known, some parents will continue to have concerns despite the evidence. In these cases, parents should be aware of the risks of serious disease in children who are not vaccinated. In some areas, outbreaks of these dangerous diseases have occurred in people who have not been immunized.

Thimerosal in vaccines

Some parents have questioned whether mercury-containing thimerosal (used as a preservative in vaccines) might cause autism. Today, with the exception of some influenza and hepatitis B vaccines, childhood vaccines used in Canada contain no thimerosal or only trace amounts. More importantly, studies have not found a link between thimerosal-containing vaccines and autism.^{footnote 3, footnote 4, footnote 1}

Vaccine combinations

Some parents also questioned whether the MMR vaccine—which combines 3 vaccines into 1 injection—causes autism since symptoms of the disorder often become apparent about the time children start getting immunized.

In response to this concern, researchers in Europe, Canada, and the United States looked closely at this issue. Studies have looked at the timing of the vaccine and the vaccine itself and have found no link between the vaccines and autism.^{footnote 5}

It's risky if you don't vaccinate your child. Immunizations are important for many reasons. Lots of research has already been done, and research continues to show that vaccines are safe.