Because vaccines are given to healthy people, including children, they must meet very high safety standards—often stricter than those for many medicines used to treat illnesses. To learn more, visit Vaccine development, approval, and safety monitoring
No. Scientific evidence clearly shows that vaccines do not cause autism. (Andersson NW et al., 2025, Taylor LE et al., 2014)
In December 2025, the WHO reviewed the evidence again and confirmed that childhood vaccines do not cause autism. (WHO.int, 2025) This supports their earlier conclusions in 2002, 2004 and 2012.
A single study published in 1998 falsely suggested a link between the MMR vaccine and autism. This study was found to be based on fake data and was withdrawn by the journal that published it. (Kmietowicz Z, 2010) The doctor who wrote it was found guilty of serious professional misconduct and lost his medical license. Since then, many large scientific studies across Europe, Canada and the United States have found no link between the MMR vaccine and autism. (Hviid A et al., 2019, Jain A et al., 2015, Uno Y et al., 2015)
More children are being diagnosed with autism today because doctors now recognize a wider range of signs. Because awareness has grown, more families are seeking assessments and support—not because vaccines have changed. (caringforkids.cps.ca, 2025)
Autism, also known as autism spectrum disorder (ASD), refers to a group of conditions that are related to the development of the brain. Autism affects how people experience the world. The abilities and needs of autistic people vary and can change over time. Some autistic people live independently, while others need lifelong care and support. The exact cause of autism is not fully known, though genetics and environmental factors likely play a role. (Scala M et al., 2025, sickkids.ca, 2025)
No. Some parents have questioned whether thimerosal (used as a preservative in some vaccines) might cause autism. Studies have not found any link between thimerosal-containing vaccines and autism or other developmental disorders. (Uno Y et al., 2015, caringforkids.cps.ca, 2025)
Today, childhood vaccines used in Canada contain no thimerosal, with the exception of some influenza (flu) vaccines.
No. Some parents have questioned whether combining measles, mumps, and rubella into one vaccine causes autism, since signs of autism often become noticeable around the same age children receive this vaccine. Researchers in Europe, Canada, and the United States have looked closely at both the timing of the vaccine and the vaccine itself, and found no link. (Demicheli V et al., 2012)
Talk to your health care provider. It is important to understand the risks of not vaccinating, which can include serious illness, hospitalization, and death—for your child and for others around them. In some areas, outbreaks of vaccine-preventable diseases have occurred among unvaccinated people, including a recent and ongoing outbreak of measles in British Columbia and many other provinces of Canada.
Parents and caregivers of unvaccinated children should also know their responsibilities as a parent of an unimmunized child.
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