Parents also worried that thiomersal (US: thimerosal - a substance that makes vaccines and other medicines usable for a longer time) might cause autism because it contains mercury. No harm from the amount of ethylmercury in vaccines was known. Yet, vaccines for infants containing mercury were taken from the market. Nevertheless, thiomersal as a cause for autism is biologically also not biologically. Mercury poisoning triggers clearly different symptoms than autism. Still, researchers did studies about this topic. They did not find a connection between thiomersal and autism.