(CNN)Dr. Anthony Fauci is urging Black Americans hesitant to take the Covid-19 vaccine to trust the process -- in part because one of the scientists at the forefront of the vaccine's development is a Black woman. The nation's top infectious disease expert, speaking at an event hosted by the National Urban League on Tuesday, said it was important to acknowledge the US history of racism in medical research and understand how that has fostered mistrust among some Black people.