evidence: These claims were made by doctor of osteopathy Rashid Buttar on 30 April 2020, during a video interview. Excerpts of the video, which have been archived here and here, have been shared across social media platforms such as Facebook many times, and the claims have been made on many other occasions by prominent individuals, such as Robert F. Kennedy Jr. and former U.S. congressman Dan Burton. Buttar rehashes the discredited yet persistent claim that vaccines cause autism, and attributes this to mercury toxicity from thimerosal. Numerous large-scale studies have already shown that there is no association between vaccines and autism[1-21]. Buttar misleadingly conflates the element mercury with the compound thimerosal. While it is true that elemental mercury is highly toxic, and that thimerosal contains this element, thimerosal has very different chemical properties. One example that illustrates the difference between elements and compounds is sodium chloride, better known as table salt. Table salt is generally harmless, whereas elemental sodium reacts violently upon contact with water and elemental chlorine was used as a chemical weapon during World War I. [...] Buttar claims that vaccines labeled thimerosal-free still contain thimerosal but provides no evidence to support his statement. He also makes several claims about the toxicity of other vaccine ingredients, namely formaldehyde, nickel, aluminum, and "DNA adducts", again without any scientific evidence. It is true that formaldehyde can be toxic and that it is used in vaccine production. However, the amount of formaldehyde present in vaccines is too low to cause toxicity. The Vaccine Education Center at the Children’s Hospital of Philadelphia states: