EXPLAINER: Is it time to get a COVID-19 booster? Which one?

FILE - This Tuesday, Jan. 5, 2021 file photo shows a vial of the Moderna COVID-19 vaccine at a pop-up vaccine clinic in Salt Lake City. U.S. regulators expect to rule Wednesday, Oct. 20, 2021 on authorizing booster doses of the Moderna and Johnson & Johnson COVID-19 vaccines, a Food and Drug Administration official said at a government meeting. (AP Photo/Rick Bowmer, File)

Millions more Americans just became eligible for COVID-19 boosters, but figuring out who’s eligible and when can be confusing. And adding to the challenge is that this time around, people can choose a different brand of vaccine for that extra dose.