The thiomersal controversy describes claims that vaccines containing the mercury-based preservative thiomersal contribute to the development of autism and other brain development disorders. Thimerosal is no longer used in children’s vaccines in the United States, except some types of flu shots. While exposure to mercurymay result in damage to brain, kidneys, and developing fetus, the current scientific consensus has found no convincing scientific evidence supporting claims that thiomersal has such effects.
Thiomersal (also spelled thimerosal, especially in the United States) is an organomercury compound used as a preservative in vaccines since the 1930s to prevent bacterial and fungal contamination. Following a mandated review of mercury-containing food and drugs in 1999, the Centers for Disease Control and Prevention(CDC) and the American Academy of Pediatrics (AAP) asked vaccine makers to remove thiomersal from vaccines as quickly as possible as a precautionary measure, and it was rapidly phased out of most US and EU vaccines, but is still used in multi-dose vials of flu vaccines in both jurisdictions. In the context of perceived increased autism rates and increased number of vaccines in the childhood vaccination schedule, some parents believed the action to remove thiomersal was an indication that the preservative caused autism.