To fight Omicron surges, some countries are handing out second booster shots. In Israel, early data suggest a fourth vaccine dose can increase protection against Covid-19, but scientists aren’t sure how long it can last and some say additional boosters won’t help. Photo composite: Eve Hartley/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 #Covid #SecondBooster #WSJ