1

Vaccines and Autism: What Colorado Families Should Know

Recent national discussions have raised understandable questions about vaccines and autism. In Colorado, we rely on decades of rigorous, global scientific research – including studies reviewed by the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) – showing that vaccines do not cause autism.

This page summarizes the facts to help families make confident, informed decisions.

What is autism?

Autism spectrum disorder (ASD) is a developmental condition that affects communication, social interaction, and behavior. Signs begin in early childhood and vary widely from person to person.

Do vaccines cause autism?

  • No. Vaccines do not cause autism.
  • Multiple large studies from around the world — involving millions of children — show no link between any vaccine and ASD.
  • Autism often becomes more noticeable around the same age children receive routine vaccines, which has led to confusion. But the timing is a coincidence, not a cause.

Does the MMR (measles, mumps, rubella) vaccine cause autism?

No. The MMR vaccine is safe and does not cause autism.

A 1998 study that claimed otherwise was later found to be fraudulent and was fully retracted. Researchers have since conducted many large, high-quality studies comparing vaccinated and unvaccinated children, and all reached the same conclusion: MMR does not increase autism risk.

Can I get the measles, mumps, and rubella vaccines separately?

No. In the United States, measles, mumps, and rubella are only available as the combined MMR or MMRV vaccines. Separate vaccines have not been shown to reduce perceived risk, and the combined vaccine is safe and effective.

Does thimerosal cause autism?

No. Thimerosal — a preservative once used in some multi-dose vaccine vials — does not cause autism.

Routine childhood vaccines in the U.S. have been thimerosal-free since 2001 (except some flu vaccine options). Autism rates did not decrease after thimerosal was removed.

Is it possible to “overwhelm” a child’s immune system with too many vaccines?

No. Babies’ immune systems handle far more antigens every day from food, air, and the environment than those in vaccines.

Studies comparing thousands of children with and without autism show they received the same total number of vaccine antigens.

Is autism becoming more common because of vaccines?

No. Autism diagnoses have increased over time because of:

  • Better screening tools.
  • Broader diagnostic criteria.
  • Increased awareness among parents and providers.

These changes explain most of the rise in ASD diagnoses. There is no evidence of an “autism epidemic.”

What are the risks of delaying or skipping vaccines?

Delaying or refusing vaccines does not prevent autism – but it does leave children at risk for serious, sometimes life-threatening infections like measles, pertussis, and chickenpox.

Vaccines are the safest and most effective way to protect children from these diseases.

Where can I learn more?