The Food and Drug Administration will have to decide the exact recipe, but a combination shot is expected that adds protection against a version of the omicron variant to the original vaccine.
Pfizer and Moderna tested shots updated to better match the omicron that surged over the winter, but that first mutant has disappeared replaced by its genetically distinct relatives. The two newest omicron cousins, called BA.4 and BA.5, together now make up half of U.S. cases, according to the Centers for Disease Control and Prevention.