New York’s sweeping vaccine mandate raises questions for companies.

The impact of the new rule will depend on answers to these questions, the DealBook newsletter writes:

• Is it legal? The city’s mandate is based on different legal considerations than the federal mandate, Lawrence Gostin, a Georgetown law professor who specializes in public health, told DealBook. “New York City has considerable home rule and very broad public health powers,” he said. But Mr. de Blasio did not get specific authorization from the City Council to enact the mandate, Mr. Gostin said, and an “inevitable avalanche of legal challenges” could argue that the mayor is overstepping. (If the federal mandate took effect, it would pre-empt anti-mandate rules at the local level, like those in Florida and Texas, but it would allow for stricter mandates like New York City’s, Mr. Gostin said.)

• What happens when Mr. de Blasio’s term ends? His successor, Eric Adams, will take office on Jan. 1 — about a week after the vaccine mandate is set to go into effect. His spokesman said that the mayor-elect would evaluate the measure once he takes office.

• What is required of companies, exactly? Kathryn Wylde, the president of the Partnership for New York City, said businesses were “blindsided” by the mandate. In an interview with DealBook, she asked: “How is it supposed to be enforced? What’s going to be the compliance procedure? What kind of records do they have to keep?” City Hall plans to release further guidelines on Dec. 15.

• Would it have an effect on labor shortages? Many of the unvaccinated workers in the city, where nearly 90 percent of adults have received at least one shot, don’t trust the system, Ms. Wylde said, “and it’s just very hard for employers to come down on them with an inflexible policy.” A group of retailers pushing back against the mandate cited labor shortages in their opposition. But others argue that mandates may make retaining employees easier. “The vast majority of employees and customers want to work or shop in a safe environment,” Mr. Gostin said. A survey of employers last month found that 3 percent of respondents with vaccine mandates had seen a surge in resignations.