Do Vaccines Cause Autism?

Reported cases of autism have been rising for several reasons, but this doesn’t necessarily mean that autism itself is becoming more common. There are a half-dozen key factors at play that explain the increase:

• Improved Awareness – More people, including parents, teachers, and doctors, recognize the signs of autism.  Consequently, better and more frequent diagnoses.

• Expanded Diagnostic Criteria – Over the years, the definition of autism has broadened to include a wider range of symptoms and severity.  This is referred to as Autism Spectrum Disorder, or ASD.

• Better Screening and Early Diagnosis – Many children are now screened for autism at an early age, allowing for earlier detection compared to past decades.

• Changes in Reporting Practices – Schools, healthcare providers, and government agencies track autism diagnoses more systematically than before.  Improved reporting results in more diagnoses. 
  

• Reduced Stigma – As society becomes more accepting of the manner an individual's brain works.  This results in more families and individuals seeking evaluations and support.

• Environmental and Genetic Factors – Some researchers have examined whether environmental influences such as parental age or prenatal factors may contribute to a genuine rise.  Causal relations are inconclusive.

Changes in diagnostic criteria have played a major role in the rising number of reported autism cases. The definition has been broadened.  Autism was first described in the 1940s, but its definition has evolved since. Previously, autism was diagnosed in individuals manifesting severe symptoms. Nowadays it includes a spectrum of behaviors ranging from mild to severe. 

The introduction of Autism Spectrum Disorder (ASD) in the DSM-5 (2013) now includes several previous diagnoses, including Asperger’s Syndrome and Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS), under one umbrella. This change meant that many people who wouldn’t have been diagnosed before were now considered autistic.

There has also been a shift from other diagnoses to autism. Before ASD was widely recognized, many children with mild social or communication difficulties were diagnosed with conditions like intellectual disability, ADHD, or speech and language disorders instead of autism. Individuals previously labeled with other conditions were reclassified as autistic.

Screening tools have improved with diagnoses being made as early as 18-24 months of age.  Before the 1990s many children with autism went undiagnosed or were diagnosed much later in life.

Finally, schools and medical institutions now have stronger incentives to diagnose autism, partly because children with ASD qualify for special education services and therapies. Better tracking and reporting of cases leaves the impression that autism is increasing dramatically.

As for the theory that vaccines are a causal factor of autism - they do not.

This misconception originated from a 1998 study by Andrew Wakefield, which was subsequently debunked and retracted due to serious flaws, unethical practices, and conflicts of interest. Since then, numerous large-scale scientific studies have found no link between vaccines and autism. Consider this:

Large studies of millions of children have confirmed that vaccines, including the MMR (measles, mumps, rubella) vaccine, do not increase autism risk.

A 2019 Danish study involving over 650,000 children found no difference in autism rates between vaccinated and unvaccinated children.

If anybody tell you that vaccines contain mercury, they're liars.  Concerns about thimerosal (a mercury-containing preservative) led to its removal from most vaccines in the early 2000s.  Autism rates continued to rise even after thimerosal was removed, proving it wasn’t a factor.

Lastly, avoid vaccines at your own peril.  The anti-vaccine movement led to outbreaks of measles, whooping cough, and other preventable diseases.  Vaccines protect children and communities from serious illnesses.

The truth of the matter is that there is no scientific evidence that vaccines cause autism. The idea has been thoroughly investigated and debunked. Vaccines are safe, effective, and essential for preventing deadly diseases.

Link to a Guest Editorial over at the New York Times.