AdvertisementCDC Tells The Vaccinated To Mask Up In Some Settings. Our Questionnaire Can Guide YouUpdated July 27, 2021Sheila Mulrooney EldredfacebookEmailTo mask or not to mask: That is the question for vaccinated people as the delta variant surges. The answer may depend on the situation, experts say. Here, these roller coaster riders mask up at Knott's Berry Farm in Buena Park, Calif. (Los Angeles Times via Getty Images)This article was originally published on July 26, 2021.