Early Data Offers Glimpse at How the Vaccinated May Fare Against Omicron

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A report out of South Africa offered a first glimpse at how vaccinated people might fare against the fast-spreading Omicron variant of the coronavirus.

Laboratory experiments found that Omicron seems to dull the power of the Pfizer-BioNTech vaccine, but also hinted that people who have received a booster shot might be better protected.

The study, published online on Tuesday, found that antibodies produced by vaccinated people were much less successful at keeping the Omicron variant from infecting cells than other forms of the coronavirus.

Scientists said the results were somewhat worrisome, but no cause for panic. The data suggests that vaccinated people might be vulnerable to breakthrough infections with Omicron, which is spreading rapidly in South Africa and has appeared in dozens of countries around the world.

But vaccines stimulate a wide-ranging immune response that involves more than just antibodies. So these experiments offer an incomplete picture of how well the vaccine protects against hospitalization or death from Omicron.

“While I think there’s going to be a lot of infection, I’m not sure this is going to translate into systems collapsing,” Alex Sigal, a virologist at the Africa Health Research Institute in Durban, South Africa, who led the research, said in an interview. “My guess is that it’ll be under control.”

Dr. Sigal and his colleagues worked at breakneck speed over the past two weeks to grow the virus and then test antibodies against it. “If I don’t die from the virus, I’ll die of exhaustion,” he said.

Originally, Dr. Sigal feared that vaccines might not provide any protection at all. It was possible that the Omicron variant had evolved a new way of entering cells, which would have rendered antibodies from vaccines useless. “Then all our efforts would be trash,” he said.

Fortunately, that proved not to be the case.

Dr. Sigal and his colleagues used antibodies from six people who received the Pfizer vaccine without ever having had Covid-19. They also analyzed antibodies from six other people who had been infected before getting the Pfizer vaccine.

The researchers found that the antibodies from all of the volunteers performed worse against Omicron than they did against an earlier version of the coronavirus. Overall, their antibodies’ potency against Omicron dropped dramatically, to about one-fortieth of the level seen when tested with an earlier version of the virus. That low level of antibodies may not protect against breakthrough Omicron infections.

Theodora Hatziioannou, a virologist at Rockefeller University who was not involved in the research, said that number was not surprising. “It’s more or less what we expected,” she said.

The results could help explain some high-profile superspreading events caused by Omicron. At an office Christmas party in Norway, the virus seems to have infected at least half of 120 vaccinated attendees.

Dr. Sigal announced the results on Twitter Tuesday afternoon.

His team found a distinct difference between the two sets of volunteers. The antibodies from the six uninfected vaccinated people were very weak against Omicron. But among the volunteers who had Covid-19 before vaccination, five out of six still produced fairly potent responses.

One reason for the difference is that people who are vaccinated after an infection produce higher levels of antibodies than do people who were not infected.

Dr. Sigal said the experiments will not be able to say much about how well boosters protect against Omicron until researchers directly test antibodies from people who have received them. But he suspected that the increased level of antibodies would provide good protection. “The more you’ve got, the better you’ll be,” he said.

Kristian Andersen, an infectious disease researcher at the Scripps Research Institute in La Jolla, Calif., who was not involved in the new study, agreed that booster shots were likely to help fend off the new variant.

“I expect boosters to restore better levels of protection,” he said. “And, importantly, early clinical data from South Africa suggest that immunity — whether from vaccines or prior infections — is still effective in preventing the more severe forms of Covid-19.”

Dr. Hatziioannou was less certain about boosters. She and her colleagues are running experiments on antibodies from boosters to test whether they will produce the same robust protection seen in people who got vaccines after infection. “I want to say yes, but we have to wait,” she said.

Pfizer and Moderna have said that they were testing their vaccines against Omicron, and that they would be able to produce vaccines specifically tailored to the variant in roughly three months.

Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Center, said that the study reinforced the need to accelerate the development of Omicron-specific shots. Even though there remains some uncertainty about how widely the variant will spread, he said, the best way of restoring protection against Omicron will be to give people a vaccine containing Omicron’s genetic information.

“Given the very large drop in neutralizing antibody titers that are seen here with Omicron,” he said, “certainly in my view it would merit pushing forward as fast as possible with making Omicron-specific vaccines, as long as it seems like there’s a possibility it could spread widely.”

The United States surgeon general on Tuesday warned that young people are facing “devastating” mental health effects as a result of the challenges experienced by their generation, including the coronavirus pandemic.

The message came as part of a rare public advisory from the nation’s top physician, Dr. Vivek H. Murthy, in a 53-page report noting that the pandemic intensified mental health issues that were already widespread by the spring of 2020.

The report cited significant increases in self-reports of depression, anxiety and emergency-room visits for mental health challenges. In the United States, emergency room visits for suicide attempts rose 51 percent for adolescent girls in early 2021 as compared with the same period in 2019. The figure rose 4 percent for boys.

Globally, symptoms of anxiety and depression doubled during the pandemic, the report noted. But mental health issues were already on the rise in the United States, with emergency room visits related to depression, anxiety and related issues up 28 percent between 2011 and 2015.

The reasons are complex and not yet definitive. Adolescent brain chemistry and relationships with friends and family are important factors, the report noted, as is a fast-paced media culture, which can leave some young minds feeling helpless.

“Young people are bombarded with messages through the media and popular culture that erode their sense of self-worth — telling them they are not good-looking enough, popular enough, smart enough or rich enough,” Dr. Murthy wrote in the report. “That comes as progress on legitimate, and distressing, issues like climate change, income inequality, racial injustice, the opioid epidemic and gun violence feels too slow.”

The surgeon general’s advisory adds to a growing number of calls for attention and action around adolescent mental health. In October, the American Academy of Pediatrics, the American Academy of Child and Adolescent Psychiatry and the Children’s Hospital Association joined to declare “a national emergency” in youth mental health.

Although blame for adolescent distress is often pinned on social media, the research suggests that screen time alone does not account for crisis. Rather, social media and other online activities act more to amplify an adolescent’s existing mental state, causing some to feel more distress and others to experience enhanced feelings of connection.

Bonnie Nagel, a pediatric neuropsychologist at Oregon Health & Science University who treats and studies adolescents, said that online interactions appear not to satisfy core needs for connection.

Recent research she co-authored shows that loneliness is a key predictor in feelings of depression and suicidal ideation.

“I don’t think it is genuine human connection when talking to somebody with a fake façade online,” Dr. Nagel said.

At the same time, screen time may be displacing activities known to be vital to physical and mental health, including sleep, exercise and in-person activity, research shows. The current generation of youth express heightened levels of loneliness — more than any other age group — despite spending countless hours connected over media.

Authorities and scientists widely acknowledge that there has been insufficient research into the underlying causes. Dr. Murthy’s advisory calls for more resources to be devoted to understanding and addressing mental health challenges, and it urges a greater appreciation of mental health as a key factor in overall health.

“This is a moment to demand change,” the report concludes.

As the world worries that the Omicron coronavirus variant may cause a surge of cases and weaken vaccines, drug developers have some encouraging news: Two new Covid-19 pills are coming soon, and are expected to work against all versions of the virus.

The Food and Drug Administration is expected to soon authorize a pill made by Merck and Ridgeback Biotherapeutics, called molnupiravir, which reduces the risk of hospitalization and death from Covid-19 by 30 percent if taken within five days of the onset of symptoms.

Another antiviral pill, developed by Pfizer, may perform even better. An interim analysis showed that the drug was 85 percent effective when taken within five days of the start of symptoms. The F.D.A. could authorize it by year’s end.

Since the start of the pandemic, scientists have hoped for convenient options like these: pills that could be prescribed by any doctor and picked up at a drugstore.

And these two pills may be just the beginning. With the threat of Omicron and other variants looming, scientists say we will need an arsenal of drugs to deploy against new foes, especially if those variants erode the protection of existing vaccines.

Researchers across the world are designing new drugs from scratch, precisely targeting weak points in the molecular structure of the coronavirus. And others are testing whether pills work better in combination than when taken on their own.

Near the end of one of the first days that 5- to 11-year-olds could get a coronavirus shot last month, Dr. Anne Steptoe, a pediatrician, sat in her cramped office cataloging the week’s patients on her laptop.

One teenage girl had been sleepless and suicidal; another was anemic. Several young boys had gained weight during the pandemic. A 10-year-old had been plagued by asthma attacks and was using her inhalers incorrectly.

The rollout of the shot for young children brought relief for many families eager to shore up protection amid a wave of new virus cases. But much of the upfront demand has already been met; many parents who were eager to get their children vaccinated have done so.

Dr. Steptoe’s patients at Charlotte Community Health Clinic, many of whom are uninsured, have chronic medical conditions, crowded housing arrangements and vulnerable family members, are among the children most in need of the shot.

Yet most parents who have brought their children to the clinic over the past month have declined it. They are wary of the vaccine, focused on getting treatment for mental and physical problems that had gone unchecked for much of the pandemic.

A pediatric vaccine kickoff event at the clinic drew just six children despite being advertised locally. Only 43 of the 900 doses the clinic received had been used as of Tuesday, and just 18 percent of 5- to 11-year-olds in Mecklenburg County, which includes Charlotte, had received an initial dose as of Nov. 29, said Dr. Raynard Washington, the county’s deputy public health director.

The U.S. government is investing $400 million in a new program to help countries get vaccines to their citizens quickly, an effort that comes amid fears that the Delta and Omicron variants will drive a new wave of cases.

The U.S. Agency for International Development said in a statement on Monday that the program, called the Initiative for Global Vaccine Access, would “enhance international coordination” to help countries “overcome vaccine access barriers.”

“As more vaccine supply flows to low- and middle-income countries, the United States and other donors must redouble efforts to help countries,” the statement said, adding that the agency would focus on countries in Africa.

Three-quarters of the money will go toward administering vaccines in remote territories and helping countries with vaccine policies and supply chain logistics, the agency said.

The rest of the money will be used to help areas where there are surges in cases and to help countries manufacture vaccines locally, the agency said.

The statement said the new funds were in addition to $1.3 billion already committed. Experts said that, in addition to donating vaccines, it is important for wealthier countries to help other countries invest in vaccine infrastructure. However, one expert said the program, known as Global Vax for short, was not quite sufficient.

“It’s not nearly enough to vastly ramp up global vaccination, but it’s a milestone,” said Lawrence O. Gostin, a Georgetown University law professor who specializes in public health.

The new program comes amid criticism that Covax, the U.N.-backed multibillion-dollar alliance, has not met its goal to acquire doses for poor countries. The alliance includes international health agencies and nonprofits whose goal is to ensure, through sheer buying power, that poor countries receive vaccines as quickly as the rich.

It was supposed to be a global powerhouse, but instead has faced months of missteps and disappointments. The alliance has had difficulty getting doses from airport tarmacs into people’s arms.

Biden administration officials say that several African nations, notably South Africa, are now turning away vaccine donations because their supply exceeds the demand — in part because of vaccine hesitancy. But global public health experts say there is another reason: Some countries are not equipped to distribute and administer the doses they receive, which often arrive on short notice.

The urgent need to vaccinate the world goes far beyond protecting people in poor nations. The longer the virus circulates, the more dangerous it can become, even for vaccinated people in wealthy countries.

Without billions more doses, experts warn, new variants could keep emerging, endangering all nations.

Sheryl Gay Stolberg contributed reporting.

Infusions of government cash that warded off an economic calamity have left millions of households with bigger bank balances than before the pandemic — savings that have driven a torrent of consumer spending, helped pay off debts and, at times, reduced the urgency of job hunts.

But many low-income Americans find their savings dwindling or even depleted. And for them, the economic recovery is looking less buoyant.

Over the past 18 months or so, experts have been closely tracking the multitrillion-dollar increase in what economists call “excess savings,” generally defined as the amount by which people’s cash reserves during the pandemic exceeded what they would have normally saved.

According to Moody’s Analytics, an economic research firm, these excess savings among many working- and middle-class households could be exhausted as soon as early next year, not only reducing their financial cushions but also potentially affecting the economy, since consumer spending is such a large share of activity.

In April 2020, after the pandemic’s outset, the nation’s personal saving rate — the percentage of overall disposable income that goes into savings each month — jumped fourfold from its February 2020 level, to 34 percent. Some of that spike resulted from government checks of up to $1,200 sent to most Americans; some simply stemmed from reduced spending during lockdowns.

The rate peaked again at 26 percent this past spring after another round of federal payments.

But the personal saving rate doesn’t account for how those savings are distributed. Wealthy households, for instance, have saved the most.

New research by the JPMorgan Chase Institute, which assesses the bank accounts of 1.6 million families, found that low-income families experienced the “greatest percent gains” during each round of stimulus, yet also exhausted their balances faster. That’s in part because those households went into the crisis with the thinnest financial buffers.

The No. 1-ranked tennis player Novak Djokovic will participate in the ATP Cup in Sydney, Australia, in January, the tournament’s organizers said on Tuesday. The announcement came after weeks of speculation about whether Djokovic would travel to Australia for the Australian Open Grand Slam because of vaccine requirements.

The ATP Cup announced that Djokovic would play on the Serbian team in the tournament, which will take place during the first nine days of the month. The cup is a precursor to the Australian Open, which will be held in Melbourne from Jan. 17 to Jan. 30. It is still unclear if Djokovic will be taking part in that competition, however. He could not immediately be reached for comment.

Australia has placed a temporary two-week ban on international arrivals because of the Omicron variant. Before that, the government announced that some categories of visa holders would be allowed to freely enter the country if they were vaccinated. Officials placed caps on the number of unvaccinated travelers who could enter the country per week, and they were required to quarantine for two weeks upon arrival.

In October, Djokovic, the reigning champion and a nine-time winner of the Australian Open, told a Serbian news outlet that he might not attend the Australian Open because he would not reveal his vaccination status.

Daniel Andrews, the premier of Victoria, the state of which Melbourne is the capital, has said that Victoria would not permit entry to unvaccinated players.

Last week, Mr. Djokovic’s father, Srdjan Djokovic, said that his son was unlikely to participate in the tournament “under these blackmails and conditions.”

Novak Djokovic’s remark in October set off rounds of contradictory statements between Australian government ministers and tournament organizers about entry requirements for international visitors.

Alex Hawk, the immigration minister, said that unvaccinated players would not be able to enter Australia.

The Women’s Tennis Association told its players in a leaked email that unvaccinated players would be allowed to enter the country, though they would have to quarantine for two weeks upon arrival.

Prime Minister Scott Morrison said something similar: Unvaccinated players would be able to enter, but would need to comply with quarantine requirements for the state in which they arrived.

In the land of opera, there is no greater social event than the annual première at Milan’s Teatro alla Scala, Italy’s pre-eminent opera house. Every year, the Dec. 7 gala opening of the season draws glitterati, Milanese A-listers and freshly minted celebrities — which these days includes the occasional virologist.

Other rank-and-file opera lovers have to settle for watching the event live on RAI 1, the national broadcaster’s flagship channel — but on Monday evening, even that felt extraordinary. Italians considered the fact that Verdi’s “Macbeth” went ahead as scheduled — and to a full house, no less — as a welcome sign of normalcy, at a time when a new wave of coronavirus infections has forced theaters in other European countries to stay shut.

It wasn’t exactly business as usual.

Masks were mandatory in the audience (though not for baritones, tenors, sopranos and other performers who roamed the stage), and access to the theater was limited to people with a Super Green Pass, as Italy’s proof of vaccination or recovery from Covid-19 is known.

“We did everything we had to do to ensure a safe environment,” Dominique Meyer, the theater’s top official, told reporters on Monday. “We’ve been very careful to protect the health of the theater workers as well as the spectators.”

Noting the safety measures, Mr. Meyer said, “If people behave seriously and with discipline, as they have until now, we can be optimistic.”

After being shut for months during the first waves of the pandemic, all 14 of Italy’s opera houses have resumed performances at full capacity. Cinemas, theaters and concert halls are also operating at full capacity, but there, too, spectators must have a Super Green Pass and wear masks.

These measures, along with other restrictions imposed last month, have made life increasingly difficult for the unvaccinated.

Silvio Brusaferro, president of the Italian National Institute of Health, told a Senate commission on Monday that 6.75 million Italians over the age of 12 had not been vaccinated. But 57 percent of Italians over 80 have received a third dose, he said.

Last year, when more stringent restrictions were still in force, La Scala was forced to limit its opening to a televised performance that featured a medley of opera and ballet. The return to something closer to normal this year elated many patrons.

“I am very happy,” the fashion designer Giorgio Armani said Monday as he arrived at the theater. “La Scala is part of Milan. We are filled with joy that culture can restart in safety.”

The World Health Organization estimated on Tuesday that by the end of the year, one in 10 people across Europe and Central Asia overall will have had a confirmed case of the coronavirus, and called on governments to speed up vaccination efforts as the world races to curb the spread of the Delta and Omicron variants.

With detected cases of the Omicron variant rising in the region as countries turn a laser focus on finding them, several countries in Europe adopted entry rules and travel bans last week, even as questions remain about the transmissibility and seriousness of Omicron. Still, the uncertainty alongside a surge of Delta variant-driven infections is fueling worries that even tougher restrictions are looming ahead of an anticipated holiday period.

Some early signs exist that Omicron may cause only mild illness, though that observation was based mainly on South Africa’s cases among young people, who are less likely overall to become severely ill from Covid. The true impact of the virus is not always felt immediately, with hospitalizations and deaths often lagging considerably behind initial outbreaks.

And at the moment, scientists say there is no reason to believe Omicron is impervious to existing vaccines, although they may turn out to be less protective to some unknown degree.

In a virtual news conference, W.H.O. experts highlighted the need for countries to escalate vaccination efforts. Vaccines are estimated to have prevented at least 470,000 deaths from December 2020 to November 2021, according to the W.H.O. and the European Center for Disease Prevention and Control.

Worldwide, about 73 percent of shots that have gone into arms have been administered in high- and upper-middle-income countries, according to the Our World in Data project at the University of Oxford. Only 0.8 percent of doses have been administered in low-income countries.

Despite the clear-cut benefits of vaccines, mandates requiring their use should be a “last resort” after all other options had been exhausted, said Dr. Hans Kluge, the organization’s Europe director. “We need to do everything possible to increase the vaccine uptake within a legal and cultural context of each specific community and country,” he said.

Dozens of countries have imposed new travel measures in response to Omicron, the agency said, but it stressed that travel bans were not effective at stemming the spread of the virus. “Disease outbreaks are contained at their source, not at their borders,” Dr. Smallwood said.

Referring to the recent trajectory of the virus overall, Dr. Kluge said the highest current rates of new cases were occurring in children, the last age group eligible to receive the vaccine.

“There will be further spread,” said Dr. Catherine Smallwood, a W.H.O. senior emergency officer, adding that the “extent and rapidity and speed of that spread is still a question.”

On Tuesday, Spain’s health ministry extended the nation’s vaccination rollout to children between 5 and 11 years of age amid concerns about the spread of the Omicron variant, particularly as more people gather for Christmas parties.

Raphael Mindercontributed reporting.

The Omicron variant is continuing to spread across communities throughout Britain, the health secretary, Sajid Javid, said, with the number of confirmed cases on Monday rising to 336 from 160 on Saturday.

“There are now 261 confirmed cases in England, 71 in Scotland and four in Wales,” Mr. Javid said in a speech Monday at the Houses of Parliament, adding that some cases had “no links to international travel.”

The sharp increase in infections came as Britain moved on Tuesday to enforce broader travel restrictions on people entering from countries that are not included on its “red list.” Vaccinated travelers aged 12 and up entering the country must now show proof of a negative P.C.R. or lateral flow test before their trip.

Previously, these vaccinated travelers were required only to self-isolate and take a coronavirus test by the second day after arrival.

Travelers from red list countries are required to quarantine in a government-approved hotel for 10 days at their own expense, where they will be required to take two P.C.R. tests.

Mr. Javid conceded that the renewed travel restrictions would “bring disruption” and “impact people’s plans to spend time with their loved ones over the festive period.” But he said that the authorities were “taking early action now so we don’t have to take tougher action later on.”

Britain continues to enforce travel restrictions on countries in Africa, most recently adding Nigeria to the red list on Monday.

Mr. Javid praised Britain’s booster program, adding that the government planned to enlist 10,000 more vaccinators and deploy approximately 350 military personnel in England this week to speed up vaccination efforts.

Until more is understood about the Omicron variant, Mr. Javid said that the measures would be temporary, and that the government would review them next week.

So far, 76 percent of Britain’s population have received a single vaccination, while 70 percent are fully vaccinated, according to Our World in Data.

At least 19 states have found the Omicron variant as it spreads rapidly throughout the United States, with Texas on Monday becoming the latest.

The Texas health authorities said in a statement that a woman in Harris County, which includes the Houston area, tested positive for Covid-19 and was found to have the Omicron variant.

“Given how quickly Omicron spread in southern Africa, we’re not surprised that it showed up here,” Dr. John Hellerstedt, the commissioner of the state’s Department of State Health Services, said in the statement.

It was not clear where the woman contracted the virus or when she tested positive. The department did not respond to requests for comment on Monday night.

Texas has now joined 18 other states that have detected the variant since Dec. 1, when the country’s first Omicron case was identified in California.

The other states are Colorado, Connecticut, Georgia, Hawaii, Louisiana, Maryland, Massachusetts, Minnesota, Mississippi, Missouri, Nebraska, New Jersey, New York, Pennsylvania, Utah, Washington and Wisconsin.

On Nov. 26, the World Health Organization named the Omicron variant, which was first detected in southern Africa, a new variant of concern.

Public health officials have said that they expected the new form of the virus to quickly find its way to the United States, despite the country’s imposition of a travel ban on international travelers from eight southern African nations, a move several other countries have also taken.

Many questions remain about the variant. There are some early indications that it may cause only mild illness, though that observation was based mainly on cases in South Africa among young people, who are generally less likely to become severely ill from Covid. Scientists are also waiting to see whether cases lead to substantial hospitalizations and deaths; both often lag surges in infections by days or weeks.

Available vaccines may still offer substantial protection against severe illness and death following infection with the variant, and federal officials are calling on vaccinated people to get booster shots.

Jesus Jiménez contributed reporting.

President Donald J. Trump’s blood oxygen level sank to a precariously low level after he announced that he had tested positive for the coronavirus last year, according to a new book by Mark Meadows, his former chief of staff.

The new details contradict Mr. Trump’s denials this year that his Covid bout was more dire than White House medical officials had acknowledged at the time.

Mr. Meadows’s book, titled “The Chief’s Chief,” goes on sale on Tuesday. He describes his tenure in the White House, alternately promoting Mr. Trump’s false claims that the 2020 election was stolen from him and attacking the news media. Mr. Meadows also revealed previously undisclosed details about the former president’s medical condition in October 2020.

Mr. Trump, who has long been fearful of appearing weak, has tried to camouflage those details. The White House staff and members of his medical team aided that effort, publicly downplaying how sick he was at the time. The former president denied a detailed New York Times report this year that he was more ill than his aides had revealed, with depressed oxygen levels and lung infiltrates, which occur when they are inflamed and filled with fluid or bacteria.

Mr. Meadows recounts in extraordinary detail how severe Mr. Trump’s illness was.

On Friday, Oct. 2, 2020, hours after the president announced on Twitter that he had tested positive for the virus, he recorded a blood oxygen level of about 86 percent, Mr. Meadows wrote. That is roughly 10 points below what would be considered normal. Most healthy people have a blood oxygen level of about 95 to 98 percent, although some people may have lower normal readings.

Mr. Trump’s health had deteriorated so much that day that members of his medical team feared they would not be able to treat him adequately without immediate attention from hospital staff, Mr. Meadows wrote.

Mayor Bill de Blasio of New York on Monday announced a sweeping coronavirus vaccine mandate for all private companies in the city. Starting Dec. 27, all employees who work in-person are required to have at least one shot of the vaccine, with no option to undergo weekly testing instead of being vaccinated.

It could be the broadest corporate vaccine mandate yet: A federal mandate for large private companies, announced by President Biden in September, has been stalled by legal challenges. New York’s mandate would apply to around 184,000 businesses.

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.