evidence: Vaccines also contain other ingredients, which help make them safer and more effective. They include: [...] Q. Are these other ingredients in vaccines safe? [...] A: Almost all childhood vaccines do NOT contain any mercury. Methylmercury, which is found in fish and other animals (including humans) can be toxic and lead to adverse effects in humans. Thimerosal, a mercury-based preservative, was removed from most childhood vaccines in 2001. Thimerosal contains a different form of mercury called ethylmercury, which is processed by the body very differently than methylmercury, and is not associated with the same adverse effects. It is still present in some influenza vaccines. Thimerosal is still used in the manufacture of some vaccines to prevent contamination. The thimerosal is removed at the end of the manufacturing process. In some cases, a tiny amount of thimerosal remains. The remaining amount is so small, that it is not possible for it to have any effect. Valid scientific studies have shown there is no link between thimerosal and autism. In fact, autism rates have actually increased since thimerosal was removed from childhood vaccines. The American Academy of Pediatrics (AAP), the American Medical Association (AMA), the CDC, and the Institute of Medicine (IOM) agree that science does not support a link between thimerosal in vaccines and autism. For the IOM report, go to http://www.iom.edu/CMS/3793/4705/4717.aspx.