There is no connection between vaccines and autism spectrum disorder.

Autism spectrum disorder (often just called autism) is a condition that affects the brain and can make it hard for those who have it to communicate and interact with other people. Experts aren't sure what causes it. 

So, how did the idea that vaccines play a role get started? Much of the blame lies with a study published in 1998 that suggested that the MMR (measles-mumps-rubella) vaccine, or infection with the naturally occurring measles virus itself, might cause autism. Since then, many scientific studies have shown that there is no link between vaccines — or any of their ingredients — and autism.

Also, the research used in that 1998 study was found to be false, the doctor who wrote it lost his medical license, and the medical journal that published it retracted the paper (this means that they believe it never should have been published).

Even with the overwhelming evidence that vaccines are safe and effective, some parents still decide not to have their children vaccinated or to delay vaccinations. But this is extremely risky — vaccine-preventable diseases like measles are still around. An unvaccinated child who gets a preventable disease could get very sick or even die, as could other people around the child.

Sometimes, kids can have a reaction to a vaccine like a mild fever or rash. But it's clear that the risk of serious reactions to the MMR and other recommended vaccines is small compared with the health risks of the often-serious diseases they prevent.

If you have concerns about any vaccine recommended for your child, talk to your doctor. Ask about the benefits and risks of each vaccine and why they're so important.