New York City Mayor Bill DeBlasio on Monday announced a Covid-19 vaccination mandate for private sector workers in the city, effective Dec. 27.

The mandate, which DeBlasio described as a “first-in-nation” policy, applies to about 184,000 businesses and expands on current requirements for municipal employees and patrons of indoor dining, entertainment and fitness establishments. Other cities and local governments across the United States are likely to follow New York’s lead, according to Steve Bell, partner in international law firm Dorsey & Whitney’s labor and employment practice.

“Of course, there will be resistance and no doubt legal objections,” Bell said in a statement. “However, the harsh realities of the seemingly more contagious omicron variant create an atmosphere in which aggressive measures may be required to halt the spread of the virus.”