“Our guidance in May said that fully vaccinated people could take off their masks safely, and that unvaccinated people should continue to wear them. Unfortunately, that’s not how it played out,” Walensky said in a phone interview with McClatchy. “Unvaccinated people took off their masks as well. And that’s what led us to where we are today.”

The CDC director said she expects a greater number of positive cases among vaccinated people – known as “breakthrough” cases – to surface in the coming weeks. As more people get vaccinated, the number of those cases will also go up, she said, especially with the amount of virus spreading throughout the country.

But the vaccines are working as intended according to the data, she said, noting that clinical trials for the vaccines produced by Pfizer and Moderna showed they were roughly 90% effective at preventing disease.