Dave Weldon, President Trump’s nominee to run the Centers for Disease Control and Prevention (CDC), told a top Democratic senator that he believes there’s a link between vaccines and autism and that the childhood vaccine schedule puts children in danger due to mercury exposure.

The U.S. Centers for Disease Control and Prevention is planning a large study into potential connections between vaccines and autism, two sources familiar with the matter told Reuters, despite extensive scientific research that has disproven or failed to find evidence of such links.