What 20th-century medical breakthrough was pioneered by Jonas Salk?

Polio vaccine

Which king turned everything he touched into gold? Who flew too close to the sun, causing his wax wings to melt? How many men did Jesus heal from leprosy with only one returning to thank Him? Which singer performed "Truth Hurts" and "About Damn Time"? In "The Star" (2017), whose birth is depicted from the animals' perspective?