John Lauerman And Angelica Lavito Bloomberg

U.S. health officials urged a pause on the use of Johnson & Johnson's Covid-19 vaccine due to dangerous blood-clotting to give them time to educate doctors on how to treat the exceedingly rare disorder.

The dose of AstraZeneca Plc's Covid vaccine that showed the highest level of effectiveness was tested in a younger population than a bigger dose that showed less efficacy, according to the head of the U.S. Operation Warp Speed program.

U.S. health officials urged a pause on the use of Johnson & Johnson's Covid-19 vaccine due to dangerous blood-clotting to give them time to educate doctors on how to treat the exceedingly rare disorder.

The dose of AstraZeneca Plc's Covid vaccine that showed the highest level of effectiveness was tested in a younger population than a bigger dose that showed less efficacy, according to the head of the U.S. Operation Warp Speed program.