Dr. Ala Stanford, a pediatric surgeon at Abington Hospital and founder of the nonprofit Black Doctors COVID-19 Consortium, is one of Fortune’s World’s 50 Greatest Leaders.

Stanford spent the early days of the coronavirus outbreak trying to provide COVID-19 tests to communities of color in the Philadelphia region.

Despite Black and Latinx residents suffering disproportionately at the time, “the majority of the testing sites were in affluent white neighborhoods,” recalled Stanford.

“There was no testing in the communities where people were dying the most,” she added. “So we created it.”

Stanford tested residents using a rented van in church parking lots. The mobile operation soon morphed into Black Doctors COVID-19 Consortium, which has drawn national attention for its efforts to treat the area’s most vulnerable and most underserved populations and to improve vaccine equity.

By early May, the group had managed to vaccinate more than 46,000 Philadelphians, with over 80 percent of them being people of color.

Stanford also drew praise from the top health officials in the Biden administration.

“She is a perfect example of how a community member can stand up and lead during a time of crisis,” said Surgeon General Vivek Murthy.

Read more about Ala Stanford in Fortune.