Delta is quickly becoming the dominant coronavirus variant in multiple countries. The variant has spread so fast because it is more contagious than the variants that came before it. At the same time, the U.S. is equipped with highly effective vaccines. Ed Yong, science writer for The Atlantic, talks with Maddie about the interaction between the variants and the vaccines and how that will be crucial in the months ahead.Reach the show by emailing shortwave@npr.org.