The link between thimerosal and autism will soon become a historical footnote. Thimerosal is a mercury-based preservative that was once used in some childhood vaccines prior to 2001. Due to the fear of potential problems resulting from this preservative, many parents declined vaccination for their children. Doctors were concerned that infectious outbreaks may start to occur in urban areas when too few people are vaccinated, so to encourage vaccination and reassure parents, thimerosal was removed from all childhood vaccines in 2001. For more discussion on the history and safety of thimerosal, please refer to Chapter 4 on vaccine safety.

Since the removal of the thimerosal preservative from vaccines, the number of children diagnosed with autism continues to rise sharply. If thimerosal were a trigger for autism, far fewer children would have been diagnosed with autism since 2000, when the preservative was removed. Unfortunately, this is not what happened. Since 2001, more and more children are diagnosed as autistic than ever before.

It would be wonderful if thimerosal were the culprit for the autism epidemic — removing it from vaccines would have stopped this childhood plague of the modern world. But autism has proven to be more complex than that. Getting rid of thimerosal has done nothing to halt the global autism epidemic.