U.S. regulators on Friday opened up COVID-19 booster shots to all adults, expanding the government’s campaign to shore up protection and get ahead of rising coronavirus cases that may worsen with the holidays. Pfizer and Moderna announced the FDA’s decision after at least 10 states already had started offering boosters to all adults. The latest action simplifies what until now has been a confusing list of who’s eligible by allowing anyone 18 or older to choose either company’s booster six months after their last dose — regardless of which vaccine they had first. But there’s one more step: The CDC must agree to expand Pfizer and Moderna boosters to even healthy young adults. Its scientific advisers were set to debate later Friday.