NEW YORK (PIX11/AP) — As concerns over COVID variants grow, outgoing New York City Mayor Bill de Blasio on Monday announced a first-in-the-nation vaccine mandate for private-sector workers across New York City. He also announced an expanded “Key to NYC” vaccine requirement to include children as young as 5 and said the pass will soon require a second dose.

De Blasio updated the city’s mandates to prevent a spike in infections during the holiday season and the colder months, the Democratic mayor said in an interview on MSNBC’s “Morning Joe.” He said, “We in New York City have decided to use a preemptive strike to really do something bold to stop the further growth of COVID and the dangers it’s causing to all of us.”

The vaccine mandate will apply to about 184,000 businesses, according to the mayor’s office. It is set to go into effect on December 27, just days before mayor-elect Eric Adams takes office. Between this new mandate and the prior mandate for all city workers, just about anyone who works in New York City will be mandated to get the shot in order to go to work.

Vaccinations are already required for hospital and nursing home workers and city employees including teachers, police officers, and firefighters. A vaccination mandate for employees of private and religious schools was announced last week.

The city moved to impose the mandate on private sector businesses even as federal courts have temporarily blocked an attempt by President Joe Biden to do the same nationally for larger companies. De Blasio said he expects the new mandate to survive any legal challenges.

Current New York City COVID-19 rules also include at least one vaccine dose for indoor restaurant dining, entertainment venues and fitness centers. Under new mandates for indoor dining, entertainment and gyms, two shots will be required for people over 12. The city is also expanding its Key to NYC vaccine mandate for city businesses, indoor dining, gyms, theaters and other entertainment venues to include children ages 5 to 11. The mayor’s office said approximately 20% of those kids have gotten at least one shot of the vaccine.

Parents will have to show proof of vaccination for those young children starting December 14. “I urge parents really strongly, get that vaccination. It’s safe. It’s been proven. Here’s another incentive to do it,” the mayor said.

De Blasio also announced that, also starting on December 14, city kids 5 to 11 will be required to get vaccinated to participate in high-risk extracurricular activities like sports, band, orchestra and dance. Key to NYC is also expanding to require proof of a second vaccine dose for all those 12 and older, except those who have received the Johnson & Johnson vaccine, de Blasio said. The initial mandate only required proof of a first vaccine dose to gain entry.

“We’ve been living with this now for most of two years,” de Blasio said. “We got to put it behind us and vaccine mandates in my experience are the one thing that really breaks through.”

When asked how the city will enforce the widespread mandate, the mayor said his office is working to put together rules now and will work with the business community. “We’ve seen a lot of cooperation so far when we put in place our mandate for example, for restaurants, indoor entertainment, indoor fitness, we actually got a lot of cooperation,” he said.

Dr. Ted Long, executive director of New York City’s Test and Trace Corps., told NEWS10’s sister station in New York City that the new mandate for private-sector workers and expanded Key to NYC requirements will help strengthen New York City and its ability to slow the spread of the virus.

“In New York City we’ve led the way for the country in terms of getting people vaccinated through mandates,” Long said. “It’s been a big credit to how we’ve been successful in New York City.”

Long pointed to the anime conference at the Javits Center as an example of how vaccination requirements work to protect New Yorkers, after a person who later tested positive for the new omicron variant attended the event.

“We’re still investigating it, but we haven’t seen evidence of widespread transmission. And if indeed, at the end of this, we still don’t see any evidence of widespread transmission, the fact that we required everybody in New York City to be vaccinated in order to go to that conference definitely helped substantially,” he said.