(Bloomberg) -- The White House has told the staff that they must again wear masks while working in the complex, according to a person familiar with matter, a symbolic setback in the fight against Covid-19 as the highly contagious delta variant spreads.

The restriction became effective on Tuesday, the person added.

The decision came after the U.S. Centers for Disease Control and Prevention tightened mask guidelines, advising that people wear them indoors in public regardless of vaccination status in places where the virus is rapidly spreading.

White House Press Secretary Jen Psaki said Tuesday that if the case rate in the nation’s capital reached a threshold established by health officials for wearing masks, “we will apply guidance accordingly.”

“That means we will be prepared to wear masks again, if required, if the guidance is leading to that, as would the president,” she said.

The White House lifted its mandate for vaccinated staff and visitors to wear masks while inside the complex in May as virus cases plummeted across the country.

Covid fatalities in the U.S. surged 48% over the past week to a daily average of 239 and hospitalizations are also on the rise. The CDC says the delta variant now makes up 83% of all sequenced Covid-19 cases in the U.S., up from 50% at the beginning of the month. Areas of the country with limited vaccination coverage are allowing spread of the highly transmissible variant.

CDC Director Rochelle Walenksy said recent data suggests that some vaccinated people who get infected with the delta variant can spread it to others.

In a written statement, President Joe Biden called new public health guidelines on masks “another step on our journey to defeating this virus.” He said he would follow it when he travels to areas with high rates of infection. Biden also said that on Thursday he would “lay out the next steps” for getting more Americans vaccinated.

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