Evidence does not link vaccines and autism
The research, explained
The best available scientific evidence shows that vaccines do not cause autism. However, it is reasonable to have questions about the benefits, risks and uncertainties of health care decisions for your family, including vaccination.
The key takeaway: evidence does not link vaccines and autism.
- Large population studies involving hundreds of thousands of children have not found that vaccination increases the risk of autism. Systematic reviews and meta-analyses have reached the same conclusion across multiple studies.
- Research has considered whether children with autism or other factors associated with autism have different vaccine safety outcomes, with no evidence.
- Recent international evidence reviews continue to find no causal relationship between vaccines and autism. Canadian public health guidance is consistent with this evidence.1
What does the research tell us?
No single study answers scientific questions about vaccine safety. Researchers look at all the evidence:
- Large population studies can compare health outcomes among vaccinated and unvaccinated children and consider factors that could influence the results.
- Systematic reviews and meta-analyses bring together findings from multiple studies and assess their quality to help researchers determine whether an apparent association is consistent and supported by reliable evidence.
A Danish study followed 657,461 children nationwide and found no increased risk of autism following the Measles, Mumps and Rubella (MMR) Vaccine. The researchers also examined children with factors associated with a higher likelihood of autism and did not find an increased risk following vaccination.2
A 2021 systematic review and meta-analysis of vaccine safety found high-strength evidence that MMR vaccines do not increase the risk of autism.3 A Cochrane review similarly found no evidence of an association between MMR vaccination and autism, based on evidence involving approximately 1.2 million children.4 Together, these studies deliver stronger evidence than an individual report.
Researchers have considered whether vaccines affect children with autism differently from those without
A 2022 study examining the safety of measles and pertussis-containing vaccines found no evidence of different safety outcomes in children with autism compared with children without autism.5
It is important to separate the causes of autism and the timing of an autism diagnosis. Autism is a neurodevelopmental condition. Characteristics of autism may become more noticeable around the same time that children receive several routine childhood vaccines. A health event occurring after vaccination does not, by itself, mean that the vaccine caused it.
What about vaccine side effects?
Vaccines, like all medical interventions, can have side effects. Most are mild and temporary, while serious adverse events can occur rarely. Vaccine safety and efficacy are continuously monitored, both before authorization and after they are in use.
Recognizing possible side effects is essential for honest communication about vaccines. It’s also important to differentiate between adverse events confirmed to be linked to vaccines and health conditions where high-quality evidence shows no causal connection. Autism, for example, is not a known side effect of vaccination.
The Public Health Agency of Canada’s Canadian Immunization Guide states that vaccines are not linked to chronic diseases such as autism and specifically notes that MMR vaccines do not cause autism. Canadian guidance also emphasizes ongoing monitoring and reporting of adverse events after immunization.6
Our approach to sharing health information
At Grandview Kids, we know that our families have questions about vaccines and other health topics. Our goal is to provide information that is evidence-informed, clear and respectful of families’ questions and experiences. We will continue to base our public health information on high-quality scientific evidence and guidance from Canadian public health authorities.
For more information, families can consult the Public Health Agency of Canada’s Canadian Immunization Guide. It’s updated regularly with new evidence. If you have questions about your child’s health, please speak with your family physician.
References
- Public Health Agency of Canada. Canadian Immunization Guide: Part 1 – Key Immunization Information: Communicating effectively about immunization. Government of Canada. Updated June 26, 2025. https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-1-key-immunization-information/page-5-communicating-effectively-immunization.html
- Hviid A, Hansen JV, Frisch M, Melbye M. Measles, mumps, rubella vaccination and autism: a nationwide cohort study. Ann Intern Med. 2019;170(8):513–520. doi:10.7326/M18-2101.
- Gidengil C, Goetz MB, Newberry S, Maglione M, Hall O, Larkin J, Motala A, Hempel S. Safety of vaccines used for routine immunization in the United States: An updated systematic review and meta-analysis. Vaccine. 2021 Jun 23;39(28):3696-3716. doi: 10.1016/j.vaccine.2021.03.079. Epub 2021 May 25. PMID: 34049735.
- Di Pietrantonj C, Rivetti A, Marchione P, Debalini MG, Demicheli V. Vaccines for measles, mumps, rubella, and varicella in children. Cochrane Database Syst Rev. 2021;11(11). doi:10.1002/14651858.CD004407.pub5.
- Zerbo O, Modaressi S, Goddard K, et al. Safety of measles and pertussis-containing vaccines in children with autism spectrum
- Public Health Agency of Canada. Canadian Immunization Guide: Part 4 – Active vaccines: Mumps vaccines. Government of Canada. Updated July 2026. https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-14-mumps-vaccine.html
