The Centers for Disease Control and Prevention said Tuesday vaccinated people living in areas with “substantial or high transmission” of COVID-19 should resume wearing masks indoors, citing the rapidly spreading and highly transmissible Delta variant for the change in guidelines. This is top White House coronavirus adviser Anthony Fauci.

Dr. Anthony Fauci: “So, when you have vaccinated people who might have a breakthrough infection, and we know now as a fact, as a scientific fact, that they can transmit the virus to an uninfected person, it’s for that reason that the CDC made the change in recommendation.”

Confirmed coronavirus cases in the U.S. have quadrupled since the start of the month. Almost two-thirds of U.S. counties qualify as high-risk areas, though new cases are particularly high in the South in states with low vaccination rates, including Arkansas, Florida, Louisiana and Missouri. The CDC also recommended everyone returning to school in the fall from kindergarten through grade 12 wear a mask indoors, including students, teachers and other staff, regardless of vaccination status. Meanwhile, the Biden administration is expected to announce that all federal employees will be required to either get vaccinated or regularly tested for COVID and be subjected to other restrictions. In other related news, Biden said so-called long COVID can be considered a disability under the Americans with Disabilities Act.