Former Centers for Disease Control and Prevention Director Susan Monarez will tell the Senate HELP Committee on Wednesday that she was fired from her post by the Trump administration last month for refusing to allow political pressure to take over the agency.

According to a copy of her testimony obtained by the Washington Examiner ahead of the hearing, Monarez will detail that she was “fired for holding the line on scientific integrity” after a clash over vaccine policy with Health and Human Services Secretary Robert F. Kennedy Jr., a longtime vaccine skeptic.