Barbara Sibley’s four New York restaurants had already weathered the city’s initial Covid-19 wave, the prevaccine surge last winter and this summer’s Delta spike when last weekend it finally happened: Fearing an outbreak and struggling with staffing after one of her workers got sick with Covid, she temporarily shut down one of her locations.

That was only the start of Ms. Sibley’s worries. She also had to weigh how long the employee, who was fully vaccinated, should isolate before returning to the job. And the messaging from public health experts was not clear-cut.

In the early days of the pandemic the Centers for Disease Control and Prevention recommended that most people who tested positive for the coronavirus isolate for 14 days. It later reduced its recommended isolation period to 10 days. But these policies were based on data from unvaccinated individuals and were implemented before the widespread availability of rapid tests. An increasing number of health and policy professionals now suggest that vaccinated people can end their isolation after five to seven days, so long as they are not symptomatic and they test negative.

On Thursday, the C.D.C. reduced, in some circumstances, the number of days it recommends that health care workers who test positive for the coronavirus isolate themselves, but it did not address other businesses.

said on Friday that fully vaccinated critical workers could return to work five days after testing positive, so long as they have no symptoms or their symptoms are resolving and they have had no fever for 72 hours. Those workers will also have to wear a mask, she said.

Omicron has intensified staffing shortages across industries, and the spike in cases has disrupted travel during the holidays, stranding thousands of customers and underscoring the economic toll of employees needing to isolate. Already, some economists are warning about the potential impact that shutdowns can have on consumer spending.

Delta Air Lines asked the C.D.C. on Tuesday to cut isolation time to five days for fully vaccinated people, warning that the current 10-day period may “significantly impact” operations. It was followed by JetBlue and Airlines for America, a trade group that represents eight airlines.

eliminated weekly testing for vaccinated players who are asymptomatic, with its chief medical officer saying the pandemic had reached a stage in which it’s unnecessary for vaccinated players to sit out if they feel healthy.

canceled performances through Christmas. CityMD, the privately owned urgent care clinic, temporarily shut 19 sites in New York and New Jersey because of staffing shortages. At least a dozen New York restaurants have temporarily closed in response to positive tests.

“I think lots of companies are looking at a lot of disruption in the next month and trying to put in policies right now, because they know their employees are going to get infected in very high numbers,” said Dr. Jha.

The United States might take direction from policy shifts abroad. Britain said on Wednesday that it was reducing to seven from 10 the days that people must isolate after showing Covid-19 symptoms.

After the British government lifted nearly all its pandemic restrictions in July, hundreds of thousands of workers were pinged by the National Health Service’s track-and-trace app and told to isolate because they had been exposed to the coronavirus. Businesses complained of being short-staffed, and economists said the “pingdemic” may have slowed economic growth in July.

In the United States, new tools to help manage through the pandemic are on the way.

The Food and Drug Administration this week authorized two pills to treat Covid, from Pfizer and Merck. Those treatments have been shown to stave off severe disease and have potential to reduce transmission of the virus, though supply of both pills, especially Pfizer’s, will be limited in the next few months.

President Biden said on Tuesday that he planned to invoke the Defense Production Act to buy and give away 500 million rapid antigen tests, a crucial tool in detecting transmissibility, though those tests will not be available for weeks or longer.

If a combination of the antiviral pills and rapid tests is able to get individuals back to work faster, “that’s a big economic point,” said Dr. Eric Topol, a professor of molecular medicine at Scripps Research.