The idea that there is mercury in vaccines causing harm to children continues to be brought up by “vaccine hesitant” groups, despite the fact that thimerosal (an ethylmercury-based preservative) was removed from all childhood vaccines in the U.S. – with the exception of multi-dose flu vials – in the early 2000s. Below are a number of resources on this issue. Please visit our topic areas on Aluminum, Formaldehyde and Vaccine Ingredients – General for more information on other ingredients in vaccines.