It’s a question laid to rest years ago, as studies showed no evidence that the preservative causes any health problems.

Thimerosal is an ingredient that helps keep vaccines pathogen free. Health and Human Services Secretary Robert F. Kennedy Jr., a noted vaccine skeptic, has falsely stated the ingredient is a contributing factor in causing autism. In recent decades, the preservative largely has been phased out of vaccines, even as autism rates continue to climb.

The U.S. Centers for Disease Control and Prevention posted a report on Tuesday that said evidence does not support a link between thimerosal-containing vaccines and autism or other neurodevelopmental disorders,