Vaccines and autism
Decades of large-scale epidemiological research across multiple countries have found no causal link between vaccines and autism spectrum disorder. The original 1998 study that sparked the controversy was retracted after being exposed as deliberate scientific fraud.
What we know
The claim that vaccines cause autism originated primarily from a 1998 Lancet paper by Andrew Wakefield, which described just twelve children and proposed a link between the MMR vaccine and a novel bowel-brain syndrome. The paper was later fully retracted after investigations revealed that Wakefield had manipulated patient data, had an undisclosed financial conflict of interest (he was being paid by lawyers preparing litigation against vaccine manufacturers), and committed ethical violations in how the children were selected and studied. The British Medical Journal published an investigation in 2011, based on journalist Brian Deer's seven-year inquiry, confirming the paper was fraudulent. The General Medical Council stripped Wakefield of his UK medical licence in 2010 for serious professional misconduct.
Since the retraction, numerous large independent studies involving millions of children across Europe, North America, and Asia have consistently found no association between any vaccine, including the MMR vaccine, and autism spectrum disorder. A widely cited 2019 Danish cohort study followed 657,461 children born between 1999 and 2010 and found no increased risk of autism among vaccinated children, including subgroups considered at higher risk. In December 2025, WHO's Global Advisory Committee on Vaccine Safety (GACVS) reviewed 31 primary research studies published between 2010 and 2025, covering data from eleven countries, and reaffirmed its conclusion that vaccines do not cause autism, consistent with its earlier reviews from 2002, 2004, and 2012.
A 2014 review by the U.S. Agency for Healthcare Research and Quality and an independent 2012 Institute of Medicine report both examined whether there was a causal relationship between autism and DTaP, HepB, Hib, IPV, and PCV vaccines, and found the evidence insufficient to support one. For the MMR vaccine specifically, the 2012 IOM report found high-strength evidence of no association based on multiple large observational studies. The proposed biological mechanisms, including thimerosal (a mercury-based preservative removed from most childhood vaccines by 2001) and aluminum adjuvants, have each been tested directly and have not shown any association with autism incidence.
The misperception persists partly because autism symptoms often become noticeable around 12 to 24 months of age, which is precisely when children receive the MMR vaccine and several other scheduled immunizations. This is a correlation that reflects developmental timing, not causation, but it created a durable and emotionally powerful impression for parents observing changes in their child around the same period. Advances in genetics have also clarified the picture: large twin and family studies estimate that 60 to 90 percent of autism risk is attributable to inherited genetic factors, and researchers have identified dozens of specific gene variants associated with autism spectrum disorder, none of which relate to vaccine exposure.
Scientific and medical consensus globally, including from WHO, the U.S. CDC, the European Medicines Agency, and national health authorities on every continent, affirms that vaccines do not cause autism, and that declining vaccination rates driven by this myth have contributed to preventable measles outbreaks in multiple countries. In 2025, this consensus came under renewed political pressure in the United States when health officials publicly questioned the settled science, prompting formal objections from major medical associations that warned the reversal was not supported by any new data and risked reversing decades of public health progress.
Common claims
- The MMR vaccine causes autismNot supported by evidence, based on a retracted, fraudulent study
- Thimerosal (mercury) in vaccines causes autismNot supported by evidence, multiple studies show no association
- Aluminum adjuvants in vaccines cause autismNot supported by evidence, large cohort studies show no association
- The original Wakefield study proved a vaccine-autism linkFalse, the study was retracted and declared fraudulent
Evidence hierarchy
All sources
- WHO GACVS: No link between vaccines and autism (December 2025)World Health Organization · 2025
- Wakefield's article linking MMR vaccine and autism was fraudulentThe BMJ · 2011
- The MMR vaccine and autism: Sensation, refutation, retraction and fraudIndian Journal of Psychiatry / PubMed Central · 2011
- Autism and Vaccines, CDCCenters for Disease Control and Prevention · 2025
- WHO MMR Vaccines and Autism, GACVSWorld Health Organization · 2003