FDA advisers voted to recommend emergency use authorization of a booster dose of Pfizer's vaccine six months after full vaccination in people 65 and older and those at high risk of severe Covid-19. CNN’s Chief Medical Correspondent Dr. Sanjay Gupta tells Anderson Cooper why the advisers didn’t recommend the booster for everyone 16 and older. Plus, CNN National Correspondent Randi Kaye gives AC360 an update on the search for Gabby Petito, the missing 22-year-old whose family last heard from her in late August. She was on a cross country road trip with her fiancé, who returned home to Florida without Petito and isn’t cooperating with the police. Airdate: September 17, 2021 Guests: Dr. Sanjay Gupta Randi Kaye To learn more about how CNN protects listener privacy, visit cnn.com/privacy