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Dr. Anthony S. Fauci, President Biden’s chief medical adviser for Covid-19, addressed reporters from the White House on Thursday, and warned the nation was “still in a very serious situation” because of the pandemic.CreditCredit…Doug Mills/The New York Times

Dr. Anthony S. Fauci, addressing reporters from the White House for the first time in months, warned Thursday that the nation is “still in a very serious situation” because of the coronavirus pandemic, but he said that so far, vaccines appear effective against new variants of the virus circulating in the United States.

Dr. Fauci, the longtime government infectious disease expert who is now President Biden’s chief medical adviser for the pandemic, said that while the number of cases appeared to be “plateauing” on a seven-day average, there were new signs of more infectious versions of the virus that could cause spikes in cases in the coming months.

He also pointed to “much more concerning mutations” in the versions of the virus circulating in South Africa and Brazil than in the variant first identified in Britain. The British version is about twice as contagious as the form of the virus that first emerged in China one year ago, and has turned up in at least 20 states in the U.S., he said. But it is not more virulent than other forms, no more likely to cause severe illness or death.

The so-called U.K. variant is more contagious because it is better at latching on to receptors in the nose, lungs and digestive tract, he said, adding that masks are now all the more essential.

So far, the variant that surfaced in South Africa has not been detected in the United States, Dr. Fauci said. But he noted that the United States has not been sequencing the genomes from virus samples to track variants “at the level that we would have liked.”

He went on to say that while some of the mutations in the variants from South Africa and Brazil may diminish the effectiveness of the Pfizer and Moderna vaccines authorized for use in the United States, the vaccines have a considerable “cushion effect,” and will still provide strong protection.

But if mutations do make it necessary to modify the vaccines, he said: “That is not something that is a very onerous thing. We can do that given the platforms we have.”

Dr. Fauci said the emergence of new variants “is all the more reason why we should be vaccinating as many people as you possibly can.” The reason is that viruses need to infect people so they can replicate and mutate. “And if you can suppress that by a very good vaccine campaign, then you could actually avoid this deleterious effect that you might get from the mutations,” he said.

If the United States can vaccinate 70 percent to 85 percent of the population by the middle or end of the summer, he predicted that “by the time we get to the fall, we will be approaching a degree of normality. It’s not going to be perfectly normal, but one that I think will take a lot of pressure off the American public.”

He added that work was still needed to instill confidence in the vaccines and persuade the public to accept them, particularly Black and Hispanic communities.

Dr. Fauci’s return to the White House briefings underscored the new scientific and political climate in Washington. Often sidelined by President Donald J. Trump, who at times threatened to fire him, he made it clear that he was happy to speak freely.

“The idea that you can get up here and talk about what you know, what the evidence, what the science is, and know that it’s, ‘Let the science speak’ — it is somewhat of a liberating feeling,” he said.

Long known for speaking his mind, and without mentioning Mr. Trump’s name, Dr. Fauci stated the obvious: Contradicting the now-former president had sometimes “got me into trouble.” He said he never liked doing so because “you didn’t feel like you could actually say something, and there wouldn’t be any repercussions.”

Asked if he felt he was back now, after essentially being banished by Mr. Trump, Dr. Fauci smiled and said, “I think so.”

Sheryl Stolberg and Apoorva Mandavilli contributed reporting.

A coronavirus testing site at Beltzville State Park in Pennsylvania on Wednesday.
Credit…Hilary Swift for The New York Times

Across the United States, prominent epidemiologists are divided over whether the country has reached a turning point in the fight against the coronavirus, though they agreed on one thing: The U.S. epidemic is not close to over, and people cannot let down their guard.

Even after its peak, any epidemic remains dangerous: Sometimes just as many people are infected after the peak as were before.

But some experts, noting that new cases are finally dropping in the majority of states, believe the epidemic is on its way out. According to a New York Times database, daily virus cases have dropped about 25 percent since Jan. 9, when they hit a seven-day average of just under 260,000. Other virus trackers have arrived at similar findings.

But some experts, looking abroad, note that new viral variants sent cases shooting upward in Britain, Ireland, South Africa and northern Brazil — and believe the United States is merely in a lull before a new spike begins.

Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota and a member of President Biden’s coronavirus advisory board, said he thought that the next three months “could be the worst part of the pandemic.”

“I hope I’m dead wrong,” he said.

Essentially, epidemiologists agree that the new variants of the virus are competing with the vaccine: whichever spreads faster will determine the course of the epidemic.

There was no agreement on when those new variants might push the case-curve upward again.

Dr. Osterholm predicted that it would happen by late February.

But Dr. Christopher J. L Murray, director of the University of Washington’s Institute for Health Metrics and Evaluation, said the variant surge in Britain seemed slower, so he predicted late March at the earliest.

If the variant found in South Africa arrives, a spike could happen faster, since that variant seems to spread more aggressively and is pushing up case counts all over southern Africa. But it has not been spotted in this United States as yet.

Although deaths in the United States are still close to the peak — a seven-day average of about 3,500 a day — most experts believe they will soon start dropping even faster than new infections, for two reasons.

One is that many nursing home patients, who have accounted for about 40 percent of all deaths, have now been vaccinated, as have some of their caregivers. The other is that as hospital caseloads ease and medical workers are under less pressure, more patients survive.

A startling new study found that Covid-19 patients in Department of Veterans Affairs hospitals were twice as likely to die if they were treated in intensive care units stretched to capacity than were those treated during quieter times.

For some experts, the big question now is whether we are at a peak, or merely on a plateau on the way up to a new one.

In the White House briefing room on Thursday, Dr. Anthony S. Fauci, the nation’s top infectious disease expert and Mr. Biden’s chief medical adviser for the pandemic, said that he thought the U.S. seven-day average of cases “looks like it might actually be plateauing.”

The dean of Brown University’s School of Public Health, Dr. Ashish K. Jha, said he hoped cases were declining permanently, given that they are dropping almost everywhere in the country, rather than merely in a few populous states.

Beyond that, he said, cellphone-movement tracking data suggests that Americans are much less on the move — and therefore spreading virus less — than they were late last year, when back-to-college travel, Thanksgiving travel and Christmas travel each drove surges in cases.

“If we can roll out the vaccine fast enough, we may stave off another surge,” Dr. Jha said.

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Dr. Anthony S. Fauci, the nation’s leading infectious disease expert, said the United States would remain in the World Health Organization and pledged commitment to international Covid-19 response.CreditCredit…Hilary Swift for The New York Times

A day after President Biden reinstated American ties with the World Health Organization, Dr. Anthony S. Fauci told the organization that the United States was committed to working closely with other nations to implement a more effective global response to the pandemic.

“Given that a considerable amount of effort will be required by all of us,” Dr. Fauci, the nation’s leading infectious disease expert, said via video link during a meeting of the group’s executive board, “the United States stands ready to work in partnership and solidarity to support the international Covid-19 response, mitigate its impact on the world, strengthen our institutions, advance epidemic preparedness for the future, and improve the health and well-being of all people throughout the world.”

Dr. Fauci said the United States would re-engage at all levels with the W.H.O. and intended to join Covax, a program set up by the agency to distribute vaccines to poorer nations.

His comments, which came exactly one year after the United States recorded its first Covid-19 case, underscored the alacrity with which the Biden administration is reversing both the substance and tone of the Trump administration’s approach.

“This is a good day for the W.H.O. and a good day for global health,” the agency’s leader, Dr. Tedros Adhanom Ghebreyesus, said, thanking Mr. Biden for honoring his pledge to resume W.H.O. membership and Dr. Fauci for his personal support to the body over many years, as well as his leadership in America’s response to the pandemic.

Mr. Biden’s decision to rejoin the W.H.O. stood in stark contrast to the approach taken by his predecessor. Mr. Trump had announced the United States would pull out of the W.H.O. in May, accusing the organization of kowtowing to China, and had sought to blame China for not doing enough to stop the spread of the virus. He had also accused Beijing of hiding the true scope of infections from the W.H.O., targeting the agency in the process.

A panel established by the organization said in a damning report that there was much blame to go around. It criticized the slow response of governments and public health organizations. Investigators, who are still working on their final report, said they could not understand why a W.H.O. committee waited until Jan. 30 to declare an international health emergency. (The Chinese government had lobbied other governments against declaring such an emergency.) The investigators also said that despite years of warnings that a pandemic was inevitable, the agency was slow to make changes.

On Thursday, addressing “my dear friend” Dr. Tedros, Dr. Fauci thanked the W.H.O. for its leadership of the global response to the pandemic. “Under trying circumstances,” he said, “this organization has rallied the scientific and research and development community to accelerate vaccines, therapies and diagnostics; conducted regular, streamed press briefings that authoritatively track global developments; provided millions of vital supplies from lab reagents to protective gear to health care workers in dozens of countries; and relentlessly worked with nations in their fight against Covid-19.”

The United States, he said, would fulfill its financial obligations to the W.H.O., halt the previous administration’s moves to draw down American staff and see technical collaboration at all levels as a fundamental part of its relationship with the agency.

Dr. Fauci also set out broader aims for increasing global pandemic preparedness, including developing an improved early warning and rapid response mechanism for dealing with biological threats, and strengthening pandemic supply chains.

“We will work with partners around the world to build a system that leaves us better prepared for this pandemic and for the next one,” he said.

A line of people waiting to receive a coronavirus vaccine at a library in Lehigh Acres, Fla., last month.
Credit…Octavio Jones for The New York Times

More than 44,000 Floridians who received the first dose of a coronavirus vaccine are overdue for their required booster shot.

That’s according to data from the Florida Department of Health, which published the numbers on Tuesday — only to stop updating the figures on Wednesday.

The state removed the information because it could cause “confusion” with guidelines from the Centers for Disease Control and Prevention, said Jason Mahon, a department spokesman.

The C.D.C. recommends getting the booster shot as close as possible to a 21-day interval for the Pfizer vaccine and a 28-day interval for the Moderna vaccine. “However, there is no maximum interval between the first and second doses for either vaccine,” says the C.D.C.

“Based on this guidance, no one is overdue for their second dose,” Mr. Mahon said in a statement.

Mr. Mahon did not answer questions about why the doses were listed as overdue in the first place. Were people missing their scheduled appointments? Or were they struggling to get appointments in Florida’s confusing patchwork system, with its limited vaccine supply?

Michael N. Teng, an assistant professor of molecular medicine at the University of South Florida who specializes in virology, said that distinction is key.

“It’s not unusual to think that people might have forgotten their appointments — that’s not uncommon,” Dr. Teng said. “But we’re postponing scheduling people for their first dose because we don’t have that many doses to give out, so there is a distribution problem at the state level right now.”

Two large private hospitals in Miami — Baptist Health and Mount Sinai Medical Center —canceled appointments en masse this week for people who had signed up to receive the first vaccine dose, citing a drop in supply. Appointments for second doses were unaffected, the hospitals said. Two city-run vaccination sites in Jacksonville will close on Friday to first-dose appointments, also because of lack of supply.

As the number of vaccines coming into Florida has shrunk, Dr. Scott Rivkees, the state surgeon general, issued a public health advisory on Thursday requiring that people provide proof of Florida residency before getting the shots, in an apparent effort to stem so-called vaccine tourism. The state has prioritized vaccinating emergency workers and people 65 and older, after nursing home residents and health care workers.

According to C.D.C. data, Florida has administered more than 1.2 million vaccine doses, out of the more than 2.5 million it has been allocated so far. That amounts to about 5.2 percent of the state’s population having received at least one dose. Only about 0.5 percent has received both doses.

If people are scheduling second-dose vaccine appointments and skipping them, they might be under the incorrect impression that receiving one dose of the vaccine is enough, Dr. Teng said. That’s not the case.

“The first dose is a priming dose that starts training the immune system,” he said. “The second dose is a booster dose that really amplifies your immune response so you make something like 10 times as many antibodies.”

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President Biden signed a string of executive orders and presidential directives on Thursday, rolling out a “full-scale, wartime” coronavirus strategy, including requiring masks on some planes, trains and buses.CreditCredit…Doug Mills/The New York Times

President Biden, pledging a “full-scale wartime effort” to combat the coronavirus pandemic, signed a string of executive orders and presidential directives on Thursday aimed at combating the worst public health crisis in a century, including new requirements for masks on interstate planes, trains and buses and for international travelers to quarantine after arriving in the United States.

“History is going to measure whether we are up to the task,” Mr. Biden declared in an appearance in the State Dining Room of the White House, with Vice President Kamala Harris and Dr. Anthony S. Fauci, his chief Covid-19 medical adviser, by his side.

With thousands of Americans dying every day from Covid-19, a national death toll that exceeds 400,000 and a new, more infectious variant of the virus spreading quickly, the pandemic poses the most pressing challenge of Mr. Biden’s early days in office. How he handles it will set the tone for how Americans view his administration going forward, as Mr. Biden himself acknowledged.

In a 200-page document released earlier Thursday called “National Strategy for the Covid-19 Response and Pandemic Preparedness,” the new administration outlines the kind of centralized federal response that Democrats have long demanded and that President Donald J. Trump refused.

Calls for unity were already fraying a day into the new administration. On Capitol Hill, Representative Steve Scalise, the No. 2 House Republican, accused the Biden team of offering “old Washington spin.” And the new president took a shot at his predecessor, saying, “For the past year we couldn’t rely on the federal government to act with the urgency and focus and coordination that we needed, and we have seen the tragic cost of that failure.”

But the Biden plan is in some respects overly optimistic and in others not ambitious enough, some experts say. It is not clear how he would enforce the quarantine requirement. And his promise to inject 100 million vaccines in his first hundred days is aiming low, since those 100 days should see twice that number of doses available.

Mr. Biden bristled at a reporter’s question when he was asked if the goal should be for a higher number. “When I announced, you all said it’s not possible,” Mr. Biden said. “Come on, give me a break, man.”

Because the currently approved coronavirus vaccines require two doses, but some Americans have already had their first shots, Mr. Biden’s promise should cover 65 million to 70 million Americans, said Scott Gottlieb, a former commissioner of the Food and Drug Administration under Mr. Trump.

“I think we can reach that goal and probably reach higher, by focusing on how many people are being vaccinated for the first time each day,” Dr. Gottlieb said. With vaccines by Pfizer and Moderna already granted emergency approval and a third, by Johnson & Johnson, likely to be authorized soon, he said, “we can definitely reach many more patients.”

Beyond the 100-day mark is where the problem lies. Federal health officials and corporate executives agree that it will be impossible to increase the immediate supply of vaccines before April at the earliest, because of lack of manufacturing capacity.

“The brutal truth is it’s going to take months before we can get the majority of Americans vaccinated,” Mr. Biden said.

It makes political sense for Mr. Biden to lower expectations, and on Capitol Hill, the new president is not getting much of a honeymoon. The No. 2 House Republican, Representative Steve Scalise of Louisiana, said in a statement, “Comments made about vaccine supply and distribution by the White House’s coronavirus czar are old Washington spin.” He added, “The fact is the Biden administration inherited contracts for 300 million doses of vaccines for two approved vaccines and two in the final stage of clinical trials.”

But the Biden team has been quick to point fingers at what they see as the Trump administration’s failures.

“What we’re inheriting is so much worse than we could have imagined,” said Jeff Zients, the new White House Covid-19 response coordinator, adding, “The cooperation or lack of cooperation from the Trump administration has been an impediment. We don’t have the visibility that we would hope to have into supply and allocations.”

In a display of his oft-stated promise to put federal health experts front and center, Mr. Biden was accompanied in the State Dining Room by Dr. Fauci and Mr. Zients. Four other officials participated by video: Xavier Becerra, the nominee for health secretary; Vivek Murthy, the nominee for Surgeon General, Dr. Rochelle Walensky, the new director of the Centers for Disease Control and Prevention; and Dr. Marcella Nunez-Smith, an adviser on racial equity in health.

Efforts to untangle and speed up the distribution of vaccines — perhaps the most pressing challenge for the Biden administration that is also the most promising path forward — will be a desperate race against time, as states across the country have warned that they could run out of doses as early as this weekend.

Though Mr. Biden has indicated his administration would release more doses as they became available and keep fewer in reserve, he said last week that he would not change the recommended timing for second doses: 21 days after the first dose for Pfizer’s vaccine, and 28 days for Moderna’s.

The administration is asking Congress for $1.9 trillion for pandemic relief, and White House officials said they would need much of that money to put their Covid-19 plan into place.

Prisoners and their families in California were angered by a plan for the correctional officers’ union to hold an in-person meeting in Las Vegas. The union changed its plans on Thursday.
Credit…Eric Risberg/Associated Press

The California correctional officers’ union planned for weeks to hold a big two-day quarterly meeting indoors and in person, despite the pandemic raging in the state’s prison system. With much of California under stay-at-home orders, the union booked the meeting in neighboring Nevada — at the Caesars Palace hotel and casino in Las Vegas.

Then on Thursday afternoon, after inmates and advocates cried foul over the risks and reporters began asking questions, the union abruptly changed course. The meeting, on Jan. 26 and 27, will now be held in California, it said, with a pledge to abide by the state’s health and safety orders.

“Infections in prisons are at an unacceptable level,” Glen Stailey, the president of the California Correctional Peace Officers Association (CCPOA), said in a statement. “We have fought for more protective measures, tests, and early vaccinations for both prison staff and incarcerated people. I recognize that our membership counts on the union’s leadership to model the strictest safety protocols. With this in mind, we are shifting the venue of our upcoming board meeting.”

Mr. Stailey added: “We’ve identified a way to hold in-person meetings — which was vital for this particular session — while strictly following the safety protocols set forth by the state government.”

According to a CCPOA spokesperson, attendees will gather in three places — Fresno, West Sacramento and Rancho Cucamonga — instead of one. They will meet in CCPOA office buildings, each member sitting in an individual office and logging onto a secure video call.

More than 45,000 inmates and nearly 15,000 guards in the California prison system have tested positive for the coronavirus, and 184 inmates and 21 guards have died, according to state data. Reports of new cases among inmates and guards have more than doubled in the past two months, according to a New York Times analysis.

Before the union switched gears, David Fathi, director of the A.C.L.U.’s National Prison Project, called the plan to meet in Las Vegas “reckless beyond belief.” And some prisoners were furious.

“We can’t even see our wives and our children and our family members,” said Johnny Collins, who is incarcerated at Ironwood State prison in Blythe, Calif. “We can’t touch them. But the correctional officers are going to do these things, and then they’re bringing the Covid back in here.”

His wife, Eileen Collins, said that incarcerated people were “fathers, grandfathers, husbands and brothers, and Covid-19 is killing them because the prison system is not designed to keep them safe.”

Prisoners across the state have complained that guards often fail to wear masks on duty, even though they are required to do so, raising concerns about how careful attendees would be at the union meeting.

Mary Dennis, who has not been able to visit her husband since last March because the state prison system has banned family visits, said she recently saw two maskless guards in her husband’s cell during a video visitation.

“If we have to have our visits taken away, why should they have a meeting?” she said.

Mr. Fathi of the A.C.L.U. compared correctional officers to nursing home workers in the risks they can pose to others. “They have the potential to expose and infect large numbers of vulnerable people in an environment where the virus can spread like wildfire,” he said.

Monica Squeri teaches a reading lesson to students in her 4th Grade class while their classmates watch remotely at James Monroe Elementary School in Edison, N.J. last November. Edison is one of a few districts that elected to maintain in person instruction for students and parents who want it.
Credit…Victor J. Blue for The New York Times

What does it mean to go to public school in the United States during the pandemic? The answer looks vastly different across the country.

With little guidance from the federal government, the nation’s 13,000 districts have largely come up with their own standards for when it is safe to open schools and what virus mitigation measures to use. Those decisions have often been based as much on politics as on public health data.

In some rural and suburban areas, especially in the South, Midwest and Great Plains, most students have studied in person, except for temporary closures during outbreaks. In many cities, the bulk of students haven’t been in a classroom since March. And in some districts, like New York City, only younger students have the option of going to school in person, with many attending only part-time.

To give readers a sense of the varying ways the pandemic has affected public education in America, The New York Times profiled seven districts across the country.

Los Angeles Unified School District, a predominantly Latino district that is the nation’s second largest, has operated remotely all fall, citing the city’s high rate of virus transmission. Cherokee County, Ga., a mostly white suburban district, offered in-person instruction all fall, until the entire district was closed as staffing shortages mounted. Wausau, Wis., a small, majority-white district in a state became one of the worst virus hot spots for a period in the fall, vacillated between in-person and remote instruction.

In the District of Columbia Public Schools, a majority Black district, we followed efforts to re-engage students during a semester of all-remote instruction. In Providence, R.I., the governor’s push for schools to open allowed its mostly Hispanic students to come back to class, unlike in other Northeastern cities.

The tiny rural Roosevelt Independent School District in West Texas, made the fraught decision to require all students to return to school in person to combat a wave of academic failures. And Edison, N.J., a large suburban district where a majority of the students are Asian, has struggled to make hybrid education work.

The series found that few districts have comprehensively assessed where their students are, and what skills they have and have not learned since schools across the country closed last March. As a result, we don’t know what approaches to remote instruction have worked or failed.

The limited data from assessments and grades this fall does, however, suggest that disadvantaged students have lost the most ground during months of remote learning.

It also seems that the vaccine will not bring a quick return of students to classrooms. More likely, many schools will continue to require masks and social distancing well into the 2021-22 school year. And while few districts have said so explicitly, many students may not see teachers or classmates in person until the fall.

The Louvre closed to the public this month in Paris.
Credit…Dmitry Kostyukov for The New York Times

European Union leaders agreed to selectively restrict nonessential travel within the bloc as well as from nonmember countries, in a bid to slow the spread of two highly contagious variants of the coronavirus that are already present in multiple countries in the region.

The leaders from the 27 nations, meeting via teleconference late Thursday, agreed to take coordinated action to manage the new variants, which scientists believe originated in Britain and in South Africa and appear to be significantly more contagious than others.

Some E.U. countries have already closed their borders with their neighbors, a move that is generally avoided in the principally borderless bloc, but has been tolerated because of the extraordinary circumstances.

“We are fully convinced that we must maintain our borders open to guarantee the good working of the internal market,” said European Council President Charles Michel at a news conference after the meeting, “but at the same time, when it comes to nonessential travel, restrictions should be considered.”

The European Union relies on open borders for trade, and it is common for people living near borders to work in the country next door. Leaders said Thursday they wanted to ensure that both trade and cross-border movement for workers were not disrupted, but that other travel deemed nonessential was minimized. The move is particularly pertinent as many schools around Europe close for a two-week break during February. Cross-border holidays during that break last year have been blamed for the rapid spread of the coronavirus across the continent.

The new measures come as cases continue to surge despite extensive measures, and compound concern on the continent where the vaccination rollout has been sluggish and is just gathering pace. Vaccination efforts suffered a hit last week when Pfizer informed countries in Europe and beyond that it would suspend production of the vaccine in its main facility in Puurs, Belgium, in order to upgrade it so it can then boost output. The company has said deliveries should resume by mid-February.

The European Commission, the bloc’s executive branch, urged authorities in member states to start carrying out wide genetic analysis on positive samples to better understand which variants are present in the region and to detect and decode emerging ones early on.

The European Centre for Disease Prevention and Control said in its latest risk analysis that E.U. countries would probably need to further tighten lockdowns to manage the spread of the variants. Most member states are in some kind of lockdown, with commercial and social life largely disrupted since late October when a second wave of the virus hit the region, causing more deaths and putting more strain on health care systems than the first wave had.

Women receiving the Sinovac Covid-19 vaccine at the Christ the Redeemer statue in Rio de Janeiro on Monday.
Credit…Ricardo Moraes/Reuters

The mayor of Rio de Janeiro announced on Wednesday that all Carnival festivities would be canceled this year as Brazil struggles with high rates of new virus cases and a lagging vaccination campaign.

Carnival festivities, which normally take place in February, were postponed in the fall, and officials had hoped that the city could hold street parades and parties in July instead. But Mayor Eduardo Paes wrote on Facebook on Wednesday that no such celebrations would be possible in 2021.

“It doesn’t make any sense to me to imagine we will have the conditions to hold carnival in July,” Mr. Paes wrote on Facebook. “Certainly in 2022 we will be able (having all been properly vaccinated) to celebrate life and our culture with all the intensity we deserve.”

Brazil’s Covid-19 death toll stands at more than 210,000, second only to the United States, and the state of Rio de Janeiro has the highest mortality rate in the country. New cases have jumped sharply in recent weeks; the country has recorded an average of 50,000 cases a day over the last week.

The country started its vaccination campaign earlier this week, but with only six million doses for a population of 213 million, picking up the pace will be difficult. Deals with vaccine manufacturers in China and India have been delayed, and it remains unclear when more doses will become available.

Brazil is also battling two new variants of the coronavirus, at least one of which is more contagious and could be contributing to the recent surge of cases. Both variants also have a mutation that may weaken the efficacy of vaccines.

Citing concern over the new variants, Britain banned flights from Latin America and Portugal, and Italy suspended flights to Brazil. But both mutated viruses had already slipped the country’s borders, and been discovered as far away as Japan and South Korea.

Global Roundup

A police cordon on a street in Shanghai following a suspected coronavirus infection on Thursday.
Credit…China Daily, via Reuters

Three locally transmitted coronavirus cases were confirmed on Thursday in Shanghai, China’s largest city, as fears rose over another large-scale outbreak in the country where the virus was first detected.

The three cases, the first in the city in about two months, were connected to prominent hospitals in the city, China’s business capital. Two of the infected individuals worked at the hospitals, one at Fudan University Shanghai Cancer Center and the other at Renji Hospital. They lived in the same residential complex. The third person was a close contact.

The infections were found during routine nucleic tests for hospital employees. The positive results led to closures at the outpatient sections of both hospitals and a citywide campaign to test all hospital employees.

Shanghai is the latest Chinese city to experience a recent outbreak, the worst since the pandemic first emerged in late 2019.

Beijing, the capital, and the provinces of Hebei, Heilongjiang, Jilin, Shanxi and Shandong have all recently reported new infections. This week alone, China reported more than 400 local infections, a steep and sudden increase.

Beijing has implemented new rules restricting the number of passengers allowed on public transportation, and extended the quarantine period for travelers returning from overseas.

Schools have been closed and the authorities on Wednesday announced that travelers returning to rural areas for the Chinese New Year holiday, the largest annual human migration in the world, must test negative for the virus and quarantine at home for 14 days.

Ma Xiaowei, the National Health Commission minister, has blamed the recent outbreak on travelers returning from overseas and on workers handling imported food.

The authorities said on Wednesday that two cases recently found in Beijing were of the more contagious B.1.1.7 variant, first found in Britain.

Here are other developments from around the world:

  • Five people were killed in a fire on Thursday that roared through an unfinished plant at the Serum Institute of India, which is producing millions of doses of the AstraZeneca and Oxford University coronavirus vaccine. Adar Poonawalla, the chief executive of Serum, the world’s largest vaccine manufacturer, said in a tweet that the destruction would not disrupt production of the vaccine, labeled Covishield in India. Covishield and a locally developed vaccine were rolled out as part of India’s massive inoculation drive this week, and Serum has promised 200 million doses to Covax, an international health group that has negotiated vaccine purchases for less wealthy countries, as soon as the end of January.

  • A senior member of South Africa’s government, Jackson Mthembu, died on Thursday from complications related to Covid-19, the office of President Cyril Ramaphosa said. Mr. Mthembu, 62, was a minister in the office of the presidency and a prominent figure in the governing African National Congress, who led media briefings on the government’s Covid-19 response. “Minister Mthembu was an exemplary leader, an activist and lifelong champion of freedom and democracy,” Mr. Ramaphosa said in a statement. It was unclear whether Mr. Ramaphosa had come into recent contact with Mr. Mthembu, who said he had tested positive on Jan. 11. But a spokesman for Mr. Ramaphosa, Tyrone Seale, said that the president was not in quarantine and that much of the government’s work had been carried out remotely.

  • Glastonbury Festival, Britain’s largest music event, has been canceled for a second year because of the Covid-19 pandemic, the organizers said on Thursday. The summer music festival has in recent years seen headline performances from Adele, The Killers and Kanye West, and usually attracts around 200,000 attendees. With Britain now under its third lockdown, Glastonbury’s organizers Michael and Emily Eavis said in a statement that it had “become clear that we will simply not be able to make the festival happen this year.” Those who paid deposits for tickets last year would now have spaces reserved in 2022, they said, when “we are very confident that we can deliver something really special.”

  • Portugal on Thursday ordered the closure of schools for at least two weeks to help stop a new wave of coronavirus infections from spreading further. Despite the country returning to nationwide lockdown last week, Prime Minister António Costa warned during a news conference that a new coronavirus variant had been spreading “significantly” since then, which required closing schools, even if there is no evidence that schools have become the epicenter of the latest infections. Mr. Costa said the variant, which originated in Britain, now accounted for 20 percent of the registered cases in Portugal, up from 8 percent last week. Mr. Costa said the school year was likely to be extended to compensate for the period of school closure.

Passengers wearing protective face masks in Berlin. Requirements on public transportation tightened this week.
Credit…Stefanie Loos/Agence France-Presse — Getty Images

As European countries brace for a potential surge of coronavirus cases linked to the new variants, countries have reimposed strict lockdown measures, and some have made “medical” grade masks mandatory in some areas.

Starting this week in Germany, N95 or surgical-grade masks are compulsory for people on public transportation, in office spaces and in shops. Such masks are also set to become mandatory in public transport and in shops in Austria next week, and France could soon follow. The French authorities are considering whether they should implement a recommendation from the country’s health advisory council that people drop homemade masks, and wear surgical or highly protective fabric masks instead.

Chancellor Angela Merkel said concerns about the new variants had driven the decision on masks.

“We have to slow the spread of this variant. That means we cannot wait until the danger is palpable,” the chancellor told reporters on Thursday, in explaining the decision to further tighten restrictions. “There is still some time to ward off the danger posed by this virus. All of the measures that we have agreed to are preventive.”

Effectively, the German authorities are trying to buy time by slowing the spread of the new variant long enough for the weather to warm and for the number of people vaccinated to increase, Ms. Merkel said. Her government has been criticized for weeks for failing to acquire enough doses of the vaccine to inoculate everyone who wants one.

The chancellor pushed back against the charge on Thursday, saying that everyone in Germany would have the opportunity to be vaccinated “by the end of the summer,” or Sept. 21. “But I cannot guarantee how many people will get themselves vaccinated,” she added.

The more contagious variant discovered in Britain has been found in 60 countries, according to the World Health Organization, but how it spreads, and whether it has already contributed to countries’ surges, remains unclear. Other variants have been detected in South Africa and in Brazil, and while none is known to be more deadly or to cause more severe disease, the authorities in some European countries have scrambled to impose measures like new mask rules or tightened lockdowns to limit their spread.

In Germany, people now have to wear N95, FFP2 or FFP3 masks, or generic surgical ones — the disposable masks that are usually blue — in some public spaces. Cloth masks and other face coverings, like face shields, are not considered sufficient and are no longer accepted in highly trafficked areas, including stores and public transportation.

The new rules imposed in Germany are tougher than guidelines from the World Health Organization, which recommends medical masks only for health care workers, people with Covid-19 symptoms and those over 60 years old or who have underlying conditions. Wearing what it calls a nonmedical mask both indoors and outdoors is enough for the general public, according to the organization.

There is widespread evidence that masks limit the risk of infection, but not all masks provide the same level of protection. A study that compared transmission rates in 16 countries and was published in The Lancet in June found that while face masks contributed to a large reduction in risk of infection, the risks were even lower when people wore a N95 mask or a similar model compared with disposable surgical masks.

N95 masks are more expensive, raising concerns that the new rules will be discriminatory for low-income families. The Austrian government has promised free masks for people on low incomes and those over 65, and Germany is making masks available to those who are vulnerable, or 60 and older.

In France, the recommendations from the country’s health advisory council are not compulsory, but the authorities could decide to make them so. At the beginning of the pandemic, French officials stumbled over recommendations on masks, and the country later faced a widespread shortage that threatened the safety of health care workers and pushed people to make their own masks. Wearing a mask in public spaces, whether indoors or outdoors, has been compulsory for months.

Neither Germany nor Britain, which in recent weeks has faced a resurgence of cases and its highest numbers of daily deaths since the beginning of the pandemic, requires people to wear masks outdoors.

A Covid-19 patient receiving treatment on Wednesday at a hospital in Milton Keynes, England. Deaths in Britain are at their highest levels of the pandemic.
Credit…Toby Melville/Reuters

When Britain’s tally of deaths from Covid-19 passed 1,000 last March, a senior health official said that it would be “a good result” to keep the eventual total below 20,000.

After two consecutive days of record death reports, the figure now stands at 93,290, the highest in Europe and the fifth highest worldwide. Speaking to reporters on Wednesday, when 1,820 deaths were reported, Prime Minister Boris Johnson described recent numbers as “appalling.”

Mr. Johnson also warned of “more to come,” as a wave of cases that began late last year, many of them from the more transmissible coronavirus variant, continues to push Britain to new extremes.

Britain has relied on national lockdown measures, implemented in early January after Mr. Johnson was forced to roll back plans for a Christmas easing of restrictions, to reduce the pressure on its National Health Service. It’s also seeking to vaccinate widely and rapidly, concentrating on first doses in a program that has so far reached 4.6 million people, about 7 percent of the population.

Though case figures have shown declines in recent days, the latest interim results from one of the country’s largest studies into coronavirus infections, released on Thursday, brought less encouraging news. Scientists said infections in England had “plateaued” at the highest levels their study had recorded so far.

“We’re not seeing the decline that we really need to see given the pressure on the N.H.S. from the current very high levels of the virus in the population,” Prof. Paul Elliott of Imperial College London, who leads the research program, told the BBC.

Looking at infections in England from Jan. 6 to 15, the report warned of a “worrying” potential uptick in cases, though it cautioned that the results do not yet reflect the impact of the latest lockdown.

“If prevalence continues at the high rate we are seeing then hospitals will continue to be put under immense pressure, and more and more lives will be lost,” Professor Elliott said in a summary of the report.

President Emmanuel Macron of France met with students at the University of Paris-Saclay on Thursday. Students are frustrated with restrictions on in-person classes.
Credit…Pool photo by Yoan Valat

President Emmanuel Macron of France tried to address growing frustration and anxiety among French university students on Thursday by vowing to allow in-person classes one day per week, subsidize mental health counseling and ramp up access to cheap cafeteria meals.

Nurseries and schools are open in France, which is not under lockdown but has enforced a 6 p.m. to 6 a.m. curfew. But university campuses have been widely closed since November and have shifted to online classes, leading many isolated students to voice growing psychological, financial and social concerns.

Hundreds of students demonstrated in front of the higher education ministry in Paris on Wednesday and expressed their anger online with the hashtag #etudiantsfantomes, or “ghost students.” Many complain of long-distance learning fatigue, intense feelings of depression and loneliness, and dwindling job prospects as France’s economy suffers the repercussions of the pandemic.

In a live discussion on Thursday at the University of Paris-Saclay, south of the French capital, students told the French president how they struggled to focus on their computer screens for hours on end. Mr. Macron said that they should be allowed to attend in-person courses one day a week as long as classroom occupancy stays below 20 percent. The timeline to implement such plans, though, would be left to individual schools.

A previous announcement by the government that only first-year university students would be able to return to campuses for small seminars had been widely criticized as insufficient.

Mr. Macron urged students to help each other cope with the pandemic, and acknowledged that young people around France were bearing the brunt of restrictions. But he warned that they would continue for several more months.

Mr. Macron, noting that the number of daily virus cases was continuing to increase amid worries over new coronavirus variants, said it wouldn’t be “reasonable” to fully reopen for the spring term.

“The return to normality won’t be until the first semester of next year,” Mr. Macron warned. “I’m going to be honest with you, the next few weeks are going to be quite hard.”

Mr. Macron promised that the government would help students pay for consultations with mental health professionals and that all students would have access to two cafeteria meals per day for 1 euro. Previously, only scholarship students had access to a single 1-euro meal per day.

The closure of bars, restaurants and cafes, as well as establishments like theaters and cinemas, has cut many university students off from much-needed part-time work, forcing some to seek help from food banks and charities to make ends meet.

A singer performing in a nightclub in Dubai in November. Dubai has been hesitant to shut down its entertainment sector but is finally enacting restrictions amid a rise in coronavirus cases.
Credit…Kamran Jebreili/Associated Press

The party is coming to an end — or, at least, to a pause — in Dubai, which allowed its hotels, restaurants and clubs to keep on offering live entertainment for the last half-year in the hope of sustaining its economically vital tourism industry. On Thursday, Dubai, one of the seven sheikhdoms that make up the United Arab Emirates, announced that it would immediately suspend issuing new entertainment permits because coronavirus cases were mounting.

The resurgence of the virus in Dubai has forced the city to backtrack on promoting itself as one of the world’s few remaining havens for fun during the coronavirus pandemic. Though it imposed a strict lockdown early on, Dubai reopened to tourists in July, and by the winter holidays, tourism had come alive again, as bars and clubs filled with people escaping lockdowns in other countries.

Dubai had reason for optimism: Industry analysts reported that hotels there were 71 percent full in December, and the emirates had begun inoculating its population with vaccines from Pfizer and Sinopharm faster than any other country except Israel. Much of the emirates’ population is young, which may have helped hold down the country’s death toll.

But as reports of new coronavirus cases began to rise in recent weeks, Dubai’s greatest source of tourists, Britain, announced that it would start requiring anyone who returned from Dubai to quarantine. Israel, which sent thousands of tourists to Dubai after the emirates and Israel agreed to normalize relations late last year, imposed the same restriction.

The emirates announced 3,529 new cases on Thursday, setting a record for the 10th straight day.

Bars and restaurants in Dubai remain open, but the city’s tourism office said it would stop issuing permits for live performances and concerts in the interest of “public health and safety.” It did not say when the permits might resume.

A teacher setting up her laptop outside of a Montessori elementary school in Chicago to begin virtual classes in solidarity with educators forced to teach inside the building on Monday.
Credit…Anthony Vazquez/Chicago Sun-Times, via Associated Press

The fight over the reopening of Chicago’s public schools escalated this week, as the governing body of the Chicago Teachers Union voted to send a resolution to its members calling on them to refuse to go to work in person starting as soon as Monday and to authorize a strike if the district locks them out of its electronic systems. Union members are voting on the resolution Thursday through Saturday.

The Chicago Public Schools, the nation’s third largest school district, began a phased reopening earlier this month, starting with prekindergarten students and some special education students, to be followed by kindergarten through eighth grade students on Feb. 1. Parents of a little more than a third of students eligible to return have opted to send their children back, while the rest chose to keep their children learning from home.

Mayor Lori Lightfoot and district leaders have argued that giving families the option to send their children back to school in person is critical to avert potential long-term harm to students’ progress. But the teachers’ union has fiercely opposed reopening, saying that returning to schools in person is not safe until cases fall and all staff members have had the opportunity to be vaccinated.

Roughly 3,800 teachers and paraprofessionals who work in prekindergarten and special education classrooms were called back to school buildings on Jan. 4, and the remainder of staff who work in kindergarten through eighth grade classrooms are expected to return to buildings on Monday.

As of last Friday, 87 teachers and paraprofessionals had refused to come to work in person and were considered absent without leave, meaning they were no longer being paid and had been locked out of district electronic systems, including those used for remote teaching.

In a statement on Wednesday night, a spokeswoman for the district said that it had agreed to the union’s safety demands at every step of the reopening process and remained committed to reaching a mutually acceptable agreement on reopening.

“CTU leadership wants to close schools that are already safely open to students, and cancel in-person learning for the tens of thousands of students who are relying on their dedicated educators to provide in-person learning in the coming weeks,” the spokeswoman, Emily Bolton, said. “Stripping tens of thousands of students of the opportunity for safe, in-person learning is not an option or a viable solution for families who have been planning to return since December.”

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Mayor Bill de Blasio urged the federal government to send New York more coronavirus vaccine doses, saying New York City is being forced to push back inoculation appointments.CreditCredit…Mary Altaffer/Associated Press

Mayor Bill de Blasio on Thursday urged the federal government to provide more coronavirus vaccine doses after he said that New York City had been forced to postpone thousands of inoculation appointments and temporarily close 15 city-run vaccine hubs this week.

“We have the staff, we have the sites, we just need the vaccine,” Mr. de Blasio said at a news conference.

New York City administered 45,000 doses on Wednesday, according to the mayor, surpassing a milestone of 500,000 doses since the vaccination drive began. He added that the city has the capacity to administer 50,000 doses per day if the supply allowed, he said.

But as much as the Biden administration has made increasing the supply of Covid-19 vaccines a central part of its strategy in fighting the coronavirus, federal health officials and corporate executives agree that it will be impossible to increase the immediate supply of vaccines before April because of lack of manufacturing capacity. The administration should first focus, experts say, on fixing the hodgepodge of state and local vaccination centers that has proved incapable of managing even the current flow of vaccines.

Both vaccines authorized by the federal government are two-dose vaccines, and New York City is expected to receive 300,000 second doses by the end of Thursday, according to Dr. Dave Chokshi, the city’s health commissioner. If individuals had a second dose appointment scheduled in the coming days, it would be honored, he said, because there was sufficient vaccine for those people to get a second dose.

“The idea is that we can continue in honoring our second dose appointments in the next few days and indeed the next few weeks, but be able to partially use that supply to administer more first doses of the vaccine with the idea that future supply will then be able to backfill our second doses over time,” Dr. Chokshi said. The city has not yet used any second doses for first doses, according to a spokeswoman from the mayor’s office.

On Thursday, Mr. de Blasio said he hoped that New York City would receive more guidance from the Biden administration on how to address the supply issue.

There is no significant reserve of vaccines to speak of. For the most part, vaccines are being shipped out each week as they are manufactured. (The exception is a small emergency stockpile that the Biden administration has said will continue.)

New York isn’t the only major American city facing a vaccine shortage.

San Francisco’s public health department expects to run out of vaccine on Thursday, The Los Angeles Times reported, because the city’s allocation dropped sharply from a week ago and the state did not replace doses that had to be discarded.

Local health officials throughout California say they have trouble scheduling appointments because they are unsure how much vaccine they will receive from week to week, the paper said.

There was one spot of good news: The California state epidemiologist cleared the use of 330,000 doses of the Moderna vaccine after the state temporarily paused distribution because of possible allergic reactions.