As highly transmissible coronavirus variants sweep across the world, scientists are racing to understand why these new versions of the virus are spreading faster, and what this could mean for vaccine efforts. New research says the key may be the spike protein, which gives the coronavirus its unmistakable shape. Illustration: Nick Collingwood/WSJ More from the Wall Street Journal: Visit WSJ.com: http://www.wsj.com Visit the WSJ Video Center: https://wsj.com/video On Facebook: https://www.facebook.com/pg/wsj/videos/ On Twitter: https://twitter.com/WSJ On Snapchat: https://on.wsj.com/2ratjSM #WSJ #Covid #Variants