Shares were down after health officials paused use of the shot over safety fears. : By Andrew Ross Sorkin, Jason Karaian, Sarah Kessler, Michael J. de la Merced, Lauren Hirsch and Ephrat Livni Federal health officials have called for an immediate halt in using Johnson & Johnson’s Covid-19 vaccine, after recipients in the U.S. suffered blood clots within two weeks of vaccination. It could mark a hurdle for America’s inoculation efforts. Six women between age 18 to 48 developed a rare disorder involving blood clots. One died and another is hospitalized in critical care.