Billions more in profits are at stake for some vaccine makers as the U.S. moves toward dispensing COVID-19 booster shots to shore up Americans’ protection against the virus. How much the manufacturers stand to gain depends on how broad the rollout proves to be. The Biden administration last month announced plans to give third doses for nearly everybody. But U.S. regulators and government advisers have rejected the across-the-board approach and instead said booster shots of Pfizer’s vaccine should go to people 65 and older and others at high risk from COVID-19. Still, some top U.S. health officials expect boosters to become broadly available in the coming weeks or months.