The Food and Drug Administration on Thursday approved updated Covid vaccines from Pfizer and Moderna, putting the new shots on track to reach most Americans in the coming days amid a summer surge of the virus. The jabs target a strain called KP.2, a descendant of the highly contagious omicron subvariant JN.1 that began circulating widely in the U.S. earlier this year. KP.2 was the dominant Covid strain in May, but now only accounts for roughly 3% of all U.S. cases as of Saturday, according to the latest Cen ...