NEW YORK — Restauranteurs in New York braced themselves Monday for a newly announced round of tighter vaccine mandates taking effect this month, during what is perhaps the worst possible time of the year for the industry.

Anyone 12 or older who wants to dine indoors at a restaurant, go to a gym or see a show will have to produce proof of having received two shots of the vaccine, up from the current one dose, Mayor Bill de Blasio announced Monday. Children ages 5 to 11 will have to show proof of at least one shot. 

De Blasio said the moves are aimed at staving off a spike of infections amid holiday gatherings and the cold weather, which drives more people indoors, where the virus can spread more easily.

Restauranteur Jeremy Wladis was worried by the change.

“It’s going to make it difficult, without a doubt,” he said. “I think it may be a little fast, it may be a little strong. And as usual, it’s ‘get the restaurants to be the policeman.’ I mean, the vaccines just became available for children recently and I can’t imagine all kids have had the opportunity to get vaccinated.”

Andrew Rigie, executive director of the New York City Hospitality Alliance, argued the changes should be delayed until after the holiday season.

“I don’t know what the exact difference would be of this smaller segment of the population to have this implemented now versus postponing it just a little bit,” Rigie said.

Mayor de Blasio is confident the new mandates will withstand any legal challenges.

“We’ve been in court many times on a variety of issues, state court, federal court – we have, every single time, been validated by the courts,” he said.

The new mandate takes effect days before de Blasio leaves office and Democrat Eric Adams is due to be sworn in. Evan Thies, a spokesman for Adams, said in a statement that the mayor-elect “will evaluate this mandate and other COVID strategies when he is in office and make determinations based on science, efficacy and the advice of health professionals.”