The CDC did not in fact find this. The CDC study President Trump is referencing found that 85 percent of a small group study reported they “always” or “often” wore a mask in the 14 days before illness onset. To get the result the president claims, you’d need to study a group entirely made up of people who wear masks, and find that 85 percent of them contracted the virus. Masks are a preventative measure and, when paired with social distancing, work even better at preventing the spread of COVID-19. Without masks, the spread of the illness would be even greater than it is today.