"This is about keeping people safe," he said. "This is about making sure our families get through COVID OK."
The new requirement will apply to all city workers, including police officers, firefighters and teachers. It will also apply to some contracted employees.
The new rule will go into effect on September 13, when students are expected to return to public schools.
Up until this point, mandating vaccines has been up to businesses to make their own policy. Local politicians are hesitant to require the shot as some constituents are in taking it. But with hospitalizations rising from coast to coast due to the highly contagious Delta variant, governments have started taking action.
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Unvaccinated Health + Hospitals employees and frontline Department of Health workers will begin the mandatory testing earlier, on August 2.
Workers in publicly run residential or congregate care facilities, like nursing homes, have to present proof of vaccination on August 16.
"We're going to keep climbing this ladder," de Blasio said, noting there could be additional mandates and enforcement as necessary.
City employees who have not been vaccinated must also wear a mask indoors at all time.
"There unfortunately will have to be consequences" for noncompliance, the mayor said.
Currently in New York City, the NYPD has 43% vaccination rate, while the Department of Corrections is at 42%. The FDNY is 55% vaccinated, while public school and city hospital staffs check in at about 60%.
Reaction the announcement was swift and varied.
"If City Hall intends to test our members weekly, they must first meet us at the table to bargain," DC37 Executive Director Henry Garrido said in a statement. "While we encourage everyone to get vaccinated and support measures to ensure our members' health and wellbeing, weekly testing is clearly subject to mandatory bargaining. New York City is a union town and that cannot be ignored."
DC347 is the city's largest public sector union.
Asked if the city has negotiated with the unions, the mayor responded, "We have the right as employers to take urgent action to protect people's health and lives."
Oren Barzilay, president of FDNY EMS Local 2507, which is separate from the Uniformed Firefighters Association, released the following statement:
"FDNY EMS Local 2507 is strongly opposed to these new workplace mandates being forced upon all 4,300 of our members by Mayor de Blasio. These must be a subject of collective bargaining. The city and the mayor cannot simply disregard the civil liberties of the workforce. The United States FDA has YET to give final approvals of the Covid-19 vaccinations and that remains troubling for some. The union is open to dialogue with the city about the details around Covid vaccinations and testing. More immediately, will testing be done on duty or has overtime been authorized to accomplish this new mandate? Will the city provide for and pay for weekly testing, or are our EMT's, Paramedics and Fire Inspectors expected to fund this out of their own pockets? Our members at FDNY EMS are highly trained medical professionals, yet they continue to be disrespected and disregarded by city leadership, which believes we can feed our families on poverty wages. Instead of dictating more royal edicts upon workers, the mayor should instead concentrate on providing more support for the women and men who serve as New York City's medical first responders. I am calling on all public employees to stand up and make their voices heard loud and clear to the Mayor."
The city's largest teachers' union, however, expressed support.
"Vaccination and testing have helped keep schools among the safest places in the city," a United Federation of Teachers spokesperson said. "This approach puts the emphasis on vaccination but still allows for personal choice and provides additional safeguards through regular testing. There are still many things to do before we are prepared to safely open our schools in September."
The announcement is the latest in a series of efforts aimed at increasing vaccination rates across the city. Last week, the mayor called on private employers to consider mandating employees get vaccinated.
"We tried purely voluntary for over half a year, we tried every form of incentive, so we have reached the limit of a purely voluntary system, it's time for more mandates," de Blasio said.
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Those remarks came just two days after de Blasio imposed the vaccinate-or-weekly-test mandate on employees of the city's public hospital system and the health department's community clinics.
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