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NEW YORK — While health officials locally and beyond work to learn more about the new omicron COVID variant, New York City’s top doctor on Monday advised all New Yorkers to mask up whenever they’re indoors in public.

Health Commissioner Dr. Dave Chokshi stressed the importance of wearing a mask, along with vaccinations and ongoing testing, alongside Mayor Bill de Blasio’s daily briefing on the city’s pandemic progress.

“When you’re indoors, regardless of whether you’re fully vaccinated or not, everyone should be wearing a mask,” Chokshi said.

While mask wearing is not required or mandated, the commissioner said it continues to be one of several things New Yorkers can do to protect themselves and others.

Chokshi confirmed there were not yet any confirmed cases of the omicron variant in the city, or country, the health department expects it could be detected locally in the coming days.

The DOH chief announced that he was issuing a Commissioner’s Advisory “strongly recommending that all New Yorkers wear a mask at all times when indoors and in a public setting – like at your grocery, building lobbies, offices and stores,” regardless of vaccination status.

He expanded on his thoughts on the new variant in a Twitter thread Monday morning, as well.

Echoing Dr. Anthony Fauci and other experts, the commissioner said there was not much evidence about omicron’s speed of spread compared to the delta variant. Similarly, there is “even less evidence” about whether or not the mutation contributes to a more, or less, severe COVID symptoms, Chokshi said.

In addition to a renewed urgency in wearing face masks indoors, the commissioner also recommended that anyone who traveled or gathered during Thanksgiving should get a COVID test.

While it’s not yet clear how well the current COVID vaccines hold up to the omicron variant, “based on what we have seen with other variants, we do expect the vaccines to retain some degree of effectiveness,” Chokshi said.

He added that cases had been rising among young children in New York City in recent weeks and urged parents to get their kids vaccinated as soon as possible.

“We still have a lot to learn about the omicron variant,” Chokshi wrote in one tweet. “But its emergence lends urgency to the importance of the precautions we’ve all become familiar with – particularly vaccination, masking and testing.”

The U.S. on Monday became one of a handful of countries reinstating travel bans in the wake of the discovery of the omicron variant.

While the U.S. and European Union members moved to prohibit only travelers from southern African nations, some countries took a more strict approach.

Japan, along with Israel and Morocco, all moved to suspend entry of all foreign visitors.

The warnings and precautions come just days after the variant was first identified by researchers in South Africa.

While the initial global response to COVID-19 was criticized as slow and haphazard, the reaction to the new variant came quickly.

The World Health Organization has praised Botswana as well as South Africa for quickly alerting the world to the presence of the new variant — and many have warned the countries should not be punished for their speed.

Cases had already been reported in EU nations Belgium, Denmark and the Netherlands before Portuguese authorities identified 13 cases of omicron among team members of the Belenenses professional soccer club. Authorities reported that one member had recently traveled to South Africa.

Despite the global worry, scientists cautioned that it is still unclear whether omicron is more alarming than other versions of the virus that has killed more than 5 million people.

Fauci said it will take about two more weeks to have more definitive information on the transmissibility, severity and other characteristics of omicron, according to the White House.

The Associated Press contributed to this report.