FILE - This Wednesday, Dec. 23, 2020 file photo shows a vial of the Moderna COVID-19 vaccine in the first round of staff vaccinations at a hospital in Denver. U.S. health advisers are debating if millions of Americans who received Moderna vaccinations should get a booster shot -- this time, using half the original dose. Already millions who got their initial Pfizer shots at least six months ago are getting a booster of that brand. On Thursday, Oct. 14, 2021, advisers to the Food and Drug Administration evaluated the evidence that Moderna boosters should be offered, too -- and on Friday, they’ll tackle the same question for those who got Johnson & Johnson’s vaccine. (AP Photo/David Zalubowski, File)