In 2008, celebrity activists and “antivaccinationists” Jim Carrey and Jenny McCarthy helped raise the alarm about the supposed dangers of vaccines. Noting the simultaneous rise in the rates of vaccine-usage and autism cases during the 20th century, they and others were convinced that mercury and other toxins used as preservatives in vaccines were causing autism. However, any fledgling scientist or statistician knows that “correlation does not imply causation,” and recent research does not indicate that vaccines are responsible for autism.
Previous research had demonstrated that children injected with vaccines containing thimerosal, a preservative that is 49 percent mercury, were no more likely to develop autism than children who were not injected. The present research, published in the journal Pediatrics, digs deeper into those findings. The scientists looked at the relationship between thimerosal exposure and autism. Additionally, researchers looked at whether it made a difference if children were exposed to mercury prenatally, or within one, seven, or 20 months of birth.
The researchers used data from the medical records of 250 kids with autism, as well as 750 kids without an autistic disorder to serve as the control population. They looked at the children’s immunization records to determine which of them had been injected with thimerosal and when.
After crunching all of the data, researchers were able to draw statistically significant conclusions. The results showed that children who had been injected with thimerosal were no more likely to have developed autism than kids who had not been injected. In fact, this result held regardless of kids’ ages when they were exposed to the chemical. The researchers even noted that half of the time they found a marginally decreased risk of children having autism after thimerosal exposure.
From a public health perspective, these results are encouraging. Parents who stop vaccinating their children invite outbreaks of virulent and deadly diseases that we haven’t faced in the U.S. for decades. Most Americans younger than 40 have never seen the horrible effects of a measles, mumps, or whooping cough outbreak, and if we continue to vaccinate, they never will. Hopefully, additional research like this study will soon put the question of whether vaccines cause autism to rest, and precious autism research dollars can be spent on finding the true causes of, and effective treatments for, the tragic disorder.