New York City Mayor Bill de Blasio announced Tuesday morning that proof of vaccination will be required to participate in indoor activities, including live performances and entertainment, a first-of-its-kind program in the U.S.

The new mandate will require vaccination for workers and customers within indoor dining, fitness and entertainment facilities, and is slated to begin rolling out the week of Aug. 16. It won’t be fully enforced until a month later, beginning Sept. 13, and is timed to school reopenings and return-to-office plans. Broadway is also slated to reopen Sept. 14.

“The only way to patronize these establishments indoors will be if you’re vaccinated — at least one dose,” de Blasio said during the press conference. “The same for folks in terms of work, they’ll need at least one dose. This is crucial because we know this will encourage a lot more vaccination.”

De Blasio confirmed the mandate will be enforced through “a strategy” dubbed “Key to NYC Pass.” The health pass — or vaccine passport — program will allow city residents to provide proof of vaccination to businesses and venues through the city’s app, the Excelsior Pass or their CDC vaccination card. “We need people to use one of those things if they want to go to indoor dining or entertainment or fitness facilities,” the mayor said.

“It’s pretty straightforward. You check someone’s vaccination status at the door,” he later added. “People check in to go to a restaurant or bar or anything. You check their vaccination status. If they have it great. If they don’t, turn around.”

De Blasio also stated that general inspections, penalties and enforcement for the initiative are not set to begin until September to allow the city and its businesses “some time to get people ready.”

The policy aims to encourage vaccination around the city amid rising COVID-19 cases, due in part to the rapid spread of the delta variant, which has become the city’s dominant strain. According to city data, just 55 percent of New Yorkers are fully vaccinated, while around 60 percent have at least one dose.

“This measure will make indoor settings where people are likely to take their mask off, they’re likely to be close together, socializing, speaking where ventilation may not be good — in short, all the conditions that the delta virus wants to spread — this initiative will make those places safer,” said Councilmember Mark Levine, who also serves as the chair of the New York City Council’s Committee on Health.

“I’m confident this will bring about an increase in vaccination at a moment when we desperately need it,” de Blasio said. “This is not an easy policy. It’s not a policy without controversy. But that has defined every difficult decision we’ve had to make in this crisis.”

As for unvaccinated children below the age of 12, de Blasio said that the city is “approaching 250,000 12- to 17-year-olds who have already been vaccinated” before confirming that within the next two weeks, his office will be working with business leaders and health officials to finalize policies around children under 12 and stressing that the focus remains on getting as many people who are currently eligible vaccinated.

“We’re focusing on where we can have an impact and that’s among those who can be vaccinated,” de Blasio said. “We’re not going to exclude those under 12. We want them to be safe, we want them to be careful. But really what we’re trying to do here is focus on the folks who could be vaccinated. The whole purpose of doing this is to give people the ultimate incentive to get vaccinated if they’re eligible.”

He later added, “We do expect in the next few months, kids in the 5 to 11 range will become eligible.”

Dr. Jay Varma, who has been the city’s main spokesperson and architect of its COVID-19 pandemic response since April 2020, also emphasized that the city will be using a layered approach — from indoor masking to “extensive improvements in indoor ventilation” — to help tackle the pandemic alongside the vaccination mandate.

De Blasio attributed the city’s decision around mandatory vaccinations for indoor activities to the private sector, including the recent announcements by fitness companies like Equinox, as well as the Broadway community. “I want to thank Equinox and SoulCycle for the decision they made about vaccine mandates,” he said. “I want to thank everyone in the Broadway community for the decision they made related to indoor performances.”

“Not everyone is going to agree with this, I understand that,” de Blasio said. “But for so many people, this is going to be the life-saving act. That we’re putting a mandate in place that is going to guarantee a much higher level of vaccination in this city — that is the key to protecting people and the key to our recovery.”

This story was originally published by The Hollywood Reporter.