LOS ANGELES (AP) — Los Angeles County’s public health officer says a rapid and sustained increase in COVID-19 cases in the nation’s largest county requires a return to mandatory mask-wearing indoors even when people are vaccinated.

Dr. Muntu Davis told a virtual press conference Thursday that a public health order requiring masks indoors will go into effect Saturday. He didn’t detail what he said would be some exceptions.

Davis says the county has been recording more than 1,000 new cases each day for a week and that there is now “substantial community transmission.”