In this episode of Take as Directed, Nellie Bristol speaks with Dr. John Vertefeuille. Dr Vertefeuille is currently the polio eradication branch chief at the Centers for Disease Control and Prevention (CDC). His long career at the CDC has included stints in Haiti, Tanzania and Nigeria. Nellie and Dr. Vertefeuille discuss why there has been an increase in vaccine-derived polio since 2016, how it differs from wild poliovirus, and how the CDC plans to contain and prevent future outbreaks.