Fact-Checked The latest guidance marks a major policy turnaround from two months ago, when the CDC announced that most people who are fully vaccinated could go without masks indoors. Patrick T. Fallon/Getty Images Based on emerging evidence on the delta variant, the Centers for Disease Control and Prevention (CDC) Tuesday recommended that fully vaccinated persons wear masks in public indoor settings in areas of substantial or high transmission. The CDC COVID Tracker currently shows that 46 percent of counties across the country have high transmission and 17 percent have substantial transmission. (The tracker allows the public to view the current status of their county.)