New York City will require all city workers to receive a coronavirus vaccine by the start of the new school year, or to present mandatory weekly coronavirus tests, Mayor Bill de Blasio announced on Monday morning.

“This is about our recovery. This is about what we need to do to bring back New York City. This is about keeping people safe,” de Blasio said at a press conference. “September is the pivot point of the recovery…and so on Sept. 13, the first day of school, every single city employee will be expected to be either vaccinated or be tested weekly.”

The new policy will apply to over 350,000 city workers, including all public school teachers and police officers. About 60 percent of Department of Education workers are vaccinated against coronavirus, a spokeswoman told the Wall Street Journal, while the NYPD said 43 percent of its service members are vaccinated.

Additionally, de Blasio said the city will require unvaccinated employees to wear a mask in indoor settings. Vaccinated employees will not be required to wear a mask if they are able to show proof of vaccination before entering their workplace.

Renee Campion, the city’s labor relations commissioner, said that unvaccinated employees who refuse to wear a mask “will not be paid” for days spent out of the office.

De Blasio has refused to implement a city-wide indoor mask mandate amid increased spread of the Delta coronavirus variant. The mayor said he would prefer that residents get vaccinated.

“I don’t want to see people say, ‘Oh, we’re wearing masks so we don’t need to deal with vaccination,'” de Blasio said last week. “We have the solution to the thing that is killing so many people and is now threatening once again our ability for people to make a living. Why is this hard? Just go get vaccinated.”