An Emergent BioSolutions lab in Baltimore.
Michael Robinson Chavez/The Washington Post, via Getty Images

Workers at a plant in Baltimore manufacturing two coronavirus vaccines accidentally conflated the ingredients several weeks ago, contaminating up to 15 million doses of Johnson & Johnson’s vaccine and forcing regulators to delay authorization of the plant’s production lines.

The plant is run by Emergent BioSolutions, a manufacturing partner to both Johnson & Johnson and AstraZeneca, the British-Swedish company whose vaccine has yet to be authorized for use in the United States. Federal officials attributed the mistake to human error.

The mix-up has delayed future shipments of Johnson & Johnson doses in the United States while the Food and Drug Administration investigates what occurred. Johnson & Johnson has moved to strengthen its control over Emergent BioSolutions’ work to avoid additional quality lapses.

The mistake is a major embarrassment both for Johnson & Johnson, whose one-dose vaccine has been credited with speeding up the national immunization program, and for Emergent, its subcontractor, which has faced fierce criticism for its heavy lobbying for federal contracts, especially for the government’s emergency health stockpile.

The error does not affect any Johnson & Johnson doses that are currently being delivered and used nationwide, including the shipments that states are counting on next week. All those doses were produced in the Netherlands, where operations have been fully approved by federal regulators.

Further shipments of the Johnson & Johnson vaccine — expected to total 24 million doses in the next month — were supposed to come from the giant plant in Baltimore. Those deliveries are now in question while the quality control issues are sorted out, according to people familiar with the matter.

Federal officials still expect to have enough doses from Johnson & Johnson and the other two approved coronavirus vaccine makers to meet President Biden’s commitment to provide enough vaccine to immunize every adult by the end of May.

Pfizer is shipping its doses ahead of schedule, and Moderna is on the verge of winning approval to deliver vials of vaccine packed with up to 15 doses instead of 10, further bolstering the nation’s stock.

The problems arose in a new plant that the federal government enlisted last year to produce vaccines from Johnson & Johnson and AstraZeneca. The two vaccines use the same technology employing a harmless version of a virus — known as a vector — that is transmitted into cells to make a protein that then stimulates the immune system to produce antibodies. But Johnson and Johnson’s and AstraZeneca’s vectors are biologically different and not interchangeable.

In late February, one or more workers somehow confused the two during the production process, raising questions about training and supervision.

Vaccine production is a notoriously fickle science, and errors are often expected to occur and ruin batches. But Emergent’s mistake went undiscovered for days until Johnson & Johnson’s quality control checks uncovered it, according to people familiar with the situation. By then, up to 15 million doses had been contaminated, the people said.

None of the doses ever left the plant, and the lot has been quarantined.

Johnson & Johnson reported the mishap to federal regulators, who then started an investigation that has delayed the authorization of that plant’s production lines. The company has beefed up the number of its own staff members who monitor Emergent’s work and instituted a variety of new checks intended to protect against future lapses.

Johnson & Johnson already faced a lag in its manufacturing that has caused the company to fall behind on its commitments to the federal government, but it seemed on track to catch up. It delivered 20 million doses by the end of March, and has pledged to deliver roughly 75 million additional doses by the end of May.

White House officials hedged their projections in a phone call with governors on Tuesday, forecasting certain deliveries from Pfizer and Moderna but warning that Johnson & Johnson’s shipments would fluctuate.

In a statement late Wednesday, the company said it expected the steps it was now taking with Emergent would enable it to deliver 24 million doses by the end of April, or about what the federal government expected. But that depends on whether Johnson & Johnson satisfies Food and Drug Administration regulators.

Paris on Wednesday night, after the curfew took effect. Dog-walking is an exception.
James Hill for The New York Times

PARIS — After more than a year of lockdowns and months of sputtering vaccination campaigns, Europe’s efforts to curb the coronavirus pandemic entered yet another difficult chapter Wednesday when President Emmanuel Macron of France announced a new set of restrictive measures in a desperate move to halt a deadly wave of infections.

The move imposed a third national lockdown, which Mr. Macron had long tried to avoid. Even so, the measures are not as strict as the national lockdown of a year ago, which kept most people indoors.

Schools and nonessential businesses will be closed across the country, travel between regions will be banned, and outdoor activities will be limited to places within six miles of home, Mr. Macron said. University students will still be allowed to attend classes one day a week.

With infections surging, hospitals crowded with patients and the virus now reaching into classrooms, Mr. Macron abandoned a gamble in which he kept France mainly open in the hope that a steady pace of vaccinations would make a lockdown unnecessary.

As the tally of coronavirus deaths relentlessly pushed close to the 100,000 mark, Mr. Macron effectively gave in to scientists and opposition politicians who have been pressing in recent weeks for a new lockdown, and added France to the list of European nations that are hunkering down again. Many of them have introduced new lockdowns in response to a wave of new cases that a slow vaccine rollout has failed to stem.

The new national restrictions take effect Saturday and will last four weeks, Mr. Macron said, adding that people who wanted to isolate themselves in a different region than where they live could still travel over the weekend to get there.

France reported on Tuesday that for the first time since last April, there were more than 5,000 people in the country’s intensive care units. France has been averaging about 37,000 new cases a day over the past week.

“The outlook is worse than frightening,” Jean-Michel Constantin, the head of the intensive care unit at the Pitié-Salpêtrière hospital in Paris, told RMC radio on Monday.

“We’re already at the level of the second wave, and we’re quickly getting close to the threshold of the first wave,” he said. “April is going to be dreadful.”

New restrictions on the regional level were introduced earlier this month, which did not stop new case reports from stubbornly rising. Pressure had been building on Mr. Macron to implement tougher measures. The steps he announced on Wednesday extend the regional restrictions nationwide.

Mr. Macron’s strategy of resisting a new lockdown seemed to be working until mid-March, when new cases rose sharply while the vaccination campaign stagnated, in part because of disarray in the rollout of the AstraZeneca vaccine. Mr. Macron’s political opponents and some scientists said he had “lost his gamble.’’

For Mr. Macron, the timing of Wednesday’s announcement was particularly significant: a year after France’s first lockdown, and a year before the next presidential election, when voters are expected to judge him largely on his handling of the epidemic and the vaccination campaign.

The health authorities said on Wednesday that about 8.5 million people, or about 13 percent of the total population, had received at least a first dose of vaccine. The government hopes to have vaccinated 10 million people by mid-April, 30 million by the summer and the whole country by the fall.

By contrast, Britain has vaccinated 46 percent of its population and the United States 29 percent, according to data from The New York Times.

Mr. Macron said on Wednesday that some cultural venues and outdoor dining at cafes and restaurants could reopen by mid-May, after the vaccine program has picked up speed.

Fans watching the Milwaukee Brewers play the Texas Rangers in a preseason baseball game at Globe Life Field in Arlington, Texas, on Monday.
Tony Gutierrez/Associated Press

President Biden said on Wednesday that the Texas Rangers’ decision to open their 43,000-seat stadium to full capacity was “not responsible” and urged Major League Baseball fans to wear masks and abide by social distancing protocols as the season begins.

“I think it’s a mistake,” Mr. Biden said of the Rangers’ plan.

“They should listen to Dr. Fauci and the scientists and the experts,” he said, referring to Dr. Anthony S. Fauci, the nation’s leading infectious disease expert. “But I think it’s not responsible.”

Speaking to ESPN the night before Opening Day, when all 30 M.L.B. teams will be in action, Mr. Biden sounded a cautious note for fans as coronavirus cases are on the rise in much of the country.

After a pandemic-shortened 2020 season, the league plans to play a full 162-game schedule with fans allowed at every game. While fans will be required to wear masks at every ballpark, policies differ based on rules in force in the city or state.

After Texas lifted coronavirus capacity restrictions in early March, the Rangers said they would allow capacity crowds at home games — the only M.L.B. franchise to do so. Fans appear to be wary. Only 12,911 spectators showed up to a Rangers exhibition game on Monday at Globe Life Field in Arlington.

Dr. Fauci said in a recent interview with the CBS program “Face the Nation” that he expected the restrictions on fans to lessen as the baseball season progressed.

But while fans may flock to stadiums on Thursday, Mr. Biden will not be throwing the first pitch at any ballparks for now.

“I know the president is eager to get out to Nationals Stadium” in Washington, Jen Psaki, the White House press secretary, said on Tuesday. “Many beautiful days, many beautiful baseball games ahead this spring.”

Taking part in the Pfizer vaccine trial at Cincinnati Children’s Hospital.
Cincinnati Children’s Hospital

The Pfizer-BioNTech Covid vaccine is extremely effective in adolescents 12 to 15 years old, perhaps even more so than in adults, the companies reported on Wednesday. No infections were found among children who received the vaccine in a recent clinical trial; they produced strong antibody responses and experienced no serious side effects.

The findings, if they hold up, may well speed a return to normalcy for millions of American families. Depending on regulatory approval, vaccinations could begin before the start of the next academic year for middle school and high school students and for elementary school children not long after.

The companies announced the results in a news release that did not include detailed data from the trial, which has not yet been peer-reviewed or published in a scientific journal.

The good news arrives even as the country records an alarming rise in infections and health officials renew calls for Americans to heed precautions and get vaccinated. On Monday, Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said that rising caseloads had left her with a sense of “impending doom.” President Biden urged Americans to keep wearing masks, whatever state officials might say.

Vaccination efforts are accelerating throughout the nation. As of Tuesday, 29 percent of Americans had received at least one dose of a coronavirus vaccine, and 16 percent had been fully inoculated, according to the C.D.C.

But the country cannot hope to reach herd immunity — the point at which immunity becomes so widespread that the coronavirus slows its crawl through the population — without also inoculating the youngest Americans, some experts say. Children under 18 account for about 23 percent of the population in the United States.

The trial included 2,260 adolescents ages 12 to 15. The children received two doses of the vaccine three weeks apart — the same amounts and schedule used for adults — or a placebo of saltwater.

The researchers recorded 18 cases of coronavirus infection in the placebo group, and none among the children who received the vaccine. Still, the low number of infections makes it difficult to be too specific about the vaccine’s efficacy in the population at large, said Angela Rasmussen, a virologist affiliated with Georgetown University.

The adolescents who received the vaccine produced nearly twice the levels of antibodies on average, compared with participants 16 to 25 years of age in an earlier trial of adults. They experienced the same minor side effects as older participants, although the companies declined to be more specific.

Akiko Iwasaki, an immunologist at Yale University, said she had expected antibody levels in adolescents to be comparable to those in young adults. “But they’re getting even better levels from the vaccines,” she said. “That’s really incredible.”

She and other experts cautioned that the vaccine might be less effective in children, and adults, against some of the variants that are circulating in the United States.

Pfizer and BioNTech have begun a clinical trial of the vaccine in children under 12 and started inoculations of children ages 5 to 11 just last week. Company scientists plan to start testing the vaccine next week in even younger children, ages 2 to 5, followed by trials in children ages 6 months to 2 years.

Pfizer and BioNTech plan to request from the Food and Drug Administration an amendment to the emergency use authorization for their vaccine, in hopes of beginning vaccinations of older children before the start of the next school year.

A nurse helping a pregnant woman at a hospital in Paris last November.
Martin Bureau/Agence France-Presse — Getty Images

More pregnant women died, experienced complications or delivered stillborn babies during the pandemic than in previous years, according to an analysis of 40 studies in 17 countries published on Wednesday in the journal Lancet Global Health.

Pregnant women face a heightened risk of severe illness and death if infected with the coronavirus. But the researchers, in Turkey and the United Kingdom, wanted to assess collateral damage from the pandemic on pregnancy and delivery, and so excluded from their analysis those studies that focused only on pregnant women who were infected.

Reviewing data on more than six million pregnancies, the investigators found evidence that disruptions to health care systems and patients’ fear of becoming infected at clinics may have led to avoidable deaths of mothers and babies, especially in low- and middle-income countries.

Data from a dozen studies showed that the chances of a stillbirth increased by 28 percent. And the risk of women dying while pregnant or during childbirth increased by more than a third in two countries: Mexico and India. A subset of studies that assessed mental health showed that postpartum depression and anxiety were also heightened during the pandemic.

Nearly six times as many women needed surgery for ectopic pregnancies — in which a fertilized egg grows outside the uterus — during the pandemic than before. Ectopic pregnancies can be treated with medications if detected early, so the results suggest that the surgeries may have resulted from delays in care.

The analysis did not find differences in other conditions associated with pregnancy, like gestational diabetes or high blood pressure, or in the rates of cesarean sections or induced labor.

The rates of preterm birth also did not change significantly during the pandemic in low- and middle-income countries. But in high-income countries, preterm births fell by nearly 10 percent.

The drop may be a result of changes in health care delivery and in pregnant women’s behavior during the pandemic, the researchers said, indicating that the pandemic has exacerbated disparities between low- and high-income countries.

The University of California at Davis campus is nearly vacant as classes are held virtually.
Max Whittaker for The New York Times

Colleges around the country have been struggling under the shadow of the coronavirus, facing declining enrollment and major budget cuts. And students have mourned the loss of the traditional college experience, grappling with the disruption as campuses closed and many classes moved on line.

But while the pandemic’s effect on ordinary college life has been widely chronicled, a new survey took a closer look at the profound effect it has had on the highest-risk students. Many, it found, have faced challenges just to make ends meet, with nearly three in five struggling for access to housing and food.

The survey of 195,000 students, released Wednesday by the Hope Center for College, Community and Justice at Temple University found that many are hard put to pay for even the most basic necessities.

“There are just way too many students who are struggling with food and housing and they’re unlikely to succeed,” said the center’s founding director, Sara Goldrick-Rab, a professor of sociology and medicine at Temple.

Students at 130 two-year colleges and 72 four-year colleges responded to the survey. Among its findings:

  • About half the respondents at four-year colleges and two in five at two-year colleges experienced housing insecurity, meaning they were not able to pay the full amount of their rent, mortgage or utility bills.

  • Students of color were more likely to experience these problems, with 70 percent of Black students and 64 percent of Hispanic students facing food insecurity, housing insecurity, or homelessness.

“The kind of resources that students have depended on, like working a job or turning to your family when you’re in a financial crisis, these things are harder now due to the pandemic,” said Dr. Goldrick-Rab.

Gov. Michelle Lujan Grisham of New Mexico receiving a vaccine in Santa Fe, N.M., last week.
Pool photo by Eddie Moore

Wyoming announced on Wednesday that residents who are at least 16 years old were now eligible for a Covid-19 vaccine in the state. New Mexico, South Dakota, Pennsylvania, Washington and Kentucky have also joined the race.

Over 40 states have now sped up their vaccination efforts at a time when health officials are warning of a possible fourth surge of coronavirus cases.

The pace of vaccinations has been picking up across the country as more states changed their eligibility timelines. As of Wednesday, an average of 2.83 million shots a day were being administered across the country, according to data reported by the Centers for Disease Control and Prevention.

“I want to take this opportunity and invite you to choose to get your free Covid-19 shot as soon as possible,” Gov. Kristi Noem of South Dakota said in announcing her state’s expansion of eligibility.

Kentucky will make the vaccine available to residents 16 and older on April 5, and Washington will do the same April 15.

“We have concerns about the trends we are seeing across the state and we must be cautious,” Gov. Jay Inslee of Washington said at a news conference on Wednesday. “Opening up full eligibility will be one tool to help in the fight against the virus.”

President Biden called earlier this month for states to open eligibility to all adults by May 1. On Monday, he directed his coronavirus response team to ensure that by April 19, there would be a vaccination site within five miles of 90 percent of Americans’ homes.

The number of Americans, and especially Black Americans, who have been vaccinated or want to be vaccinated has risen significantly since January, according to a recent poll by the Kaiser Family Foundation. The survey also found that Republicans and white evangelical Christians continue to be skeptical of getting a virus vaccine.

Ms. Noem, a Republican who leads a Republican-majority state, acknowledged those concerns on Wednesday.

“There will never be the heavy hand of government mandating that you get the vaccine,” she said. “We will trust our people to do the right thing.”

Gov. Andrew M. Cuomo at his office in New York this month.
Seth Wenig/Agence France-Presse — Getty Images

As the coronavirus subsided in New York last year, Gov. Andrew M. Cuomo had begun pitching a book proposal that would center on his image as a hero of the pandemic. But by early last summer, both his book and image had hit a critical juncture.

An impending Health Department report threatened to disclose a far higher number of nursing home deaths related to the coronavirus than the Cuomo administration had previously made public. Melissa DeRosa and other top aides expressed concern about the higher death toll, and, after their intervention, the number was removed from the final version.

At stake was not just the governor’s reputation, but also, potentially, a huge payoff: a book deal that ended with a high offer of more than $4 million, according to people with knowledge of the bidding process.

On Wednesday, Richard Azzopardi, a senior adviser to the governor, rejected any link between Mr. Cuomo’s book and the Health Department report.

“There is no connection between the report and this outside project, period,” Mr. Azzopardi said. “And any suggestion otherwise is just wrong.”

The book, “American Crisis: Leadership Lessons From the Covid-19 Pandemic,” was a dramatic retelling of the battle against the virus in a state where nearly 50,000 people have died.

Emails and an early draft of Mr. Cuomo’s book obtained by The New York Times indicate that the governor was writing it as early as mid-June, relying on a cadre of trusted aides and junior staffers for everything from full-scale edits to minor clerical work, potentially running afoul of state laws prohibiting use of public resources for personal gain.

Ms. DeRosa also had significant input on the July 6 report issued by the Department of Health, which basically cleared Mr. Cuomo’s administration of fault in its handling of nursing homes — discounting the impact of a March 2020 state memo that had asked such facilities to take in or readmit residents who had tested positive for the disease.

In two earlier drafts of the report, which were both reviewed by The Times, the second sentence said that “from March 1, 2020, through June 10, 2020, there were 9,844 fatalities among NYS nursing home residents with confirmed or suspected COVID-19.” The 9,844 fatalities were far higher than the 6,432 nursing home deaths used in the state’s final report.

Mr. Cuomo, 63, has declined to confirm exactly how much he was paid for “American Crisis,” which was published in October.

Around 48,000 hardcover copies have been sold, according to NPD BookScan, but sales have staggered because of scandals surrounding Mr. Cuomo’s administration. In early March, Crown Publishing Group said that it would stop promoting “American Crisis,” because of a federal investigation into the withholding of data. The imprint also canceled plans for a paperback edition.

Mr. Cuomo’s draft of “American Crisis” contained some nuggets of self-reflection, including a take on his televised briefings last year, which garnered him a great deal of popularity in the early days of the pandemic.

“People are smart,” the governor wrote. “And after a while if they can watch you long enough, they can figure out who you are.”

Peter Navarro speaking  to reporters outside the White House in October 2020.
Anna Moneymaker for The New York Times

The Trump administration was so slow to prepare for the coronavirus pandemic that a top aide to President Donald J. Trump took matters into his own hands.

That aide, Peter Navarro, Mr. Trump’s deputy assistant and trade adviser, personally steered hundreds of millions of dollars in contracts for pandemic supplies to politically connected or novice companies, a preliminary investigation by House Democrats has found.

Mr. Navarro sounded an early alarm about supply shortages, according to emails and other documents released by a House committee overseeing the federal coronavirus response. In a memo dated March 1, 2020, he complained that “movement has been slow.”

After that, documents show, he prodded the Federal Emergency Management Agency to award a $96 million sole-source contract for respirators to AirBoss Defense Group, a defense industry supplier, telling a company executive “everything you requested is OK,” even though no contract had been signed.

The agency awarded the sole-source contract six days later. AirBoss was represented by a retired Army general, Jack Keane, who had been awarded the Presidential Medal of Freedom by Mr. Trump just days before the contract was issued

In a statement, Mr. Navarro said he wanted to move aggressively to combat the threat of the virus.

“In a war, you need to move with warp speed,” he wrote. “My mission was to assist the president in saving lives, which we undeniably did. Given the same set of facts, I would do everything exactly the same. Full stop!”

But the Democrats, led by Representative James C. Clyburn of South Carolina, the No. 3 House Democrat, questioned Mr. Navarro’s efforts.

They noted that officials in Mr. Navarro’s office had coordinated with executives at the Eastman Kodak Company, best known for its photography business, which then entered into a letter of intent in June 2020 to collaborate on the domestic manufacture of pharmaceutical agents, even though the company had no experience in that field.

Mr. Navarro also pushed for the Trump administration to award a $354 million contract to Phlow, a brand-new company in Richmond, Va., to manufacture generic medicines and pharmaceutical ingredients — an effort aimed at building up an American manufacturing base for products that were needed to treat Covid-19 but were made overseas. The Democrats’ investigation found that Mr. Navarro had been introduced to Phlow’s chief executive in November 2019.

“My head is going to explode if this contract does not get immediately approved,” Mr. Navarro wrote to top federal health officials in March 2020. “This is a travesty. I need PHLOW noticed by Monday morning. This is being screwed up. Let’s move this now. We need to flip the switch and they can’t move until you do. FULL funding as we discussed.”

People who just received a vaccine exiting the Javits Center on Tuesday in Manhattan.
James Estrin/The New York Times

Even as much of the rest of the country has had a reprieve, New York City has remained a coronavirus hot spot, with new cases holding level, often at about 25,000 a week.

As variants and vaccinations have taken hold, public health experts have debated what to call the current, confusing phase of the epidemic, when cases remain alarmingly high, but hope is drawing nearer.

“The term I’ve been using is ‘high plateau’,” said Dr. Jay Varma, a senior adviser for public health at City Hall. “We’re basically trying to come down off of our second wave and what we’re trying desperately to do is prevent a third wave.”

Since mid-February, the seven-day average of new cases in the city has largely remained between 3,500 and 4,000.

Epidemiologists and disease modelers spoke of a stalemate between the pace of vaccinations and the momentum of two new, more contagious variants that were spreading steadily across the city. Those variants now make up a majority of cases, city officials said.

Several public health experts who use prediction models believe that New York’s current upswing probably won’t reach levels that the city saw during the peak after the holiday season, when cases surged to nearly 6,500 per day on average. But the cases aren’t likely to drop much soon either.

Dr. Ronald Scott Braithwaite, a professor at N.Y.U. Grossman School of Medicine who has been modeling New York City’s epidemic and is an adviser to the city, predicted that cases would gradually rise — “not so much a wave, but a bulge,” he said — for a month or two until a critical number of people had been vaccinated.

“At our current rate of vaccination, it seems it will be mid- to late May before vaccinations win the tug of war,” Dr. Braithwaite said.

On Monday, state officials announced that all adults in New York would be eligible for vaccination starting next week, which should boost the vaccination effort as supply begins to increase.

The new normal for New York City, at least until mid-May, may well be an average positive test rate that hovers around 6 percent and a daily case rate of around 4,000.

Wan Yang, a professor of epidemiology at Columbia University’s Mailman School of Public Health, said that changing social behavior might be the tipping point that leads to a sustained upswing in cases. She noted that New York’s restrictions had eased over the past month — including looser limits around indoor dining and the reopening of indoor fitness classes — and that many New Yorkers were socializing and interacting more than before.

Tracey Tully contributed reporting.

Republican lawmakers meet during the first 2021-22 legislative session in the Assembly Chambers at the Wisconsin State Capitol in Madison.
Amber Arnold/Wisconsin State Journal, via Associated Press

The Wisconsin Supreme Court struck down a statewide mask order on Wednesday, concluding by a 4-3 vote that Gov. Tony Evers exceeded his powers in issuing it.

The ruling comes the same week that President Biden urged states to maintain or reimpose mask mandates, and federal health officials have warned of a possible fourth surge of the virus.

Coronavirus cases around the country have started rising again in some states, including Wisconsin, where the number of new virus cases has shot up 34 percent over the past two weeks, according to a New York Times database.

The ruling delivered the latest mask reversal in the state since its original order went into effect in August. Since then, the mask order has been extended, suspended and reinstated multiple times.

In February the Republican-led State Legislature repealed the governor’s original mandate. Mr. Evers, a Democrat, issued a new mask order an hour later, an action the Wisconsin Supreme Court said on Wednesday was unlawful.

The justices on the court are elected to 10-year terms, and though the races are technically nonpartisan, they have been bitterly contested in recent years on partisan and ideological lines. Conservatives now outnumber more liberal justices, 4 to 3, and voted together on the mask ruling.

The majority wrote in the ruling that “the question in this case is not whether the governor acted wisely; it is whether he acted lawfully. We conclude he did not.”

Responding to the decision, Mr. Evers said in a statement that the state’s fight against the virus was not over. “While we work to get folks vaccinated as quickly as we can, we know wearing a mask saves lives, and we still need Wisconsinites to mask up so we can beat this virus and bounce back from this pandemic,” he said.

Though the United States is in far better shape now than it was in January, when new cases, hospitalizations and new deaths peaked, health officials say that relaxing proven measures like mask-wearing now could jeopardize the recent progress. They have urged Americans to hold on a little longer.

Even so, some governors have recently lifted mask orders after seeing declines in virus cases and deaths.

“This is a critical moment in our fight against the pandemic, as we see increases in cases, we can’t afford to let our guard down,” Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, said on Wednesday at a White House news conference, referring broadly to the current state of the pandemic in the United States. She said the country is close to seeing life return to normal.

“We’re not quite there yet,” she said. “We need to keep taking the mitigation measures like wearing a mask and social distancing as we continue to get more and more Americans vaccinated.”

Wisconsin announced on Tuesday that all residents 16 years and older would be eligible for vaccinations beginning April 5, joining dozens of other states that have accelerated plans for vaccinating all adults. Federal health officials have said that speeding up vaccinations is one of the best ways to fight potential virus surges, particularly as new variants make their way around the country.

In Wisconsin, 31 percent of the state’s total population had received at least one dose of a vaccine as of Tuesday, on par with the national average of about 29 percent, according to a New York Times Times analysis of data from the Centers for Disease Control and Prevention.

Andrés R. Martínez contributed reporting.

Hollywood High Teachers Assistant Yolanda Franco conducts class remotely in Los Angeles, California.
Rodin Eckenroth/Getty Images

The coronavirus pandemic has taken an “alarming” toll on Los Angeles students, leaving nearly two-thirds of kindergartners behind in the skills necessary to learn reading, and about 40,000 high school students at risk of not graduating over the next four years, an early analysis of educational data from the nation’s second-largest public school system has found.

The report, based on publicly available data from the Los Angeles Unified School District, was released Wednesday by Great Public Schools Now, a nonprofit advocacy group backed by California philanthropies that favor charter schooling.

The findings add to mounting evidence that when schools shifted to remote instruction last year, students paid in lost academic progress, emotional and developmental setbacks and widened achievement gaps.

The report is “a call to action for L.A.U.S.D. and all education systems to develop a comprehensive educational recovery plan now,” said Ana F. Ponce, the organization’s executive director and a parent of a third-grader in the district.

The Los Angeles school system is California’s largest, serving more than 650,000 students more than 80 percent of whom are Black, Latino or low income. Instruction for the overwhelming majority has been online since last March and students are only this month beginning to return to classrooms.

The Great Public Schools report, using the district’s data and learning assessments, found that during the early months of the pandemic, as the district scrambled to shift to online instruction, “two out of five middle and high school students were absent every day from the district’s online learning program, Schoology.”

Of the students who did log on, only 36 percent actively engaged daily in online instruction, according to the data, and some elementary students were entirely absent for the last several months of that school year. Even after a system was in place for the fall semester and attendance improved, the report said, more than one-third of the district’s enrollment — tens of thousands of students — were still failing to actively engage on a daily basis.

Attendance was lower among Black, Latino and low-income students, as well as among students who had disabilities or housing issues, who were in foster care, or who were learning English. As of February, some 23,000 students still were regularly missing three or more days a week of classes and some 9,000 were absent for weeks at a time — so disengaged that they did not click even once on the district’s online platform.

Grade school literacy assessments showed that only 43 percent of Black students and only 44 percent of Latino students were on track in reading, and huge numbers of high school students have fallen so far behind in credits toward graduation that they may not earn their high school diplomas. Among them, the researchers reported, are more than 40 percent of the Los Angeles Unified Class of 2022.

The group recommends that as vaccines and health measures make classrooms safer, the district should prioritize live time with teachers, increase counseling and mental health services and accelerate classwork to get students caught up, rather than get bogged down in more time-consuming traditional remedial classes. The group also advises the district to use a planned expansion of summer school to assess and develop individual learning plans for each student.

Stay-at-home orders and bans on indoor restaurant dining during the pandemic disrupted many people’s eating patterns, experts say.
Spencer Platt/Getty Images

Experts who treat eating disorders like anorexia, bulimia and binge-eating disorder are reporting an overwhelming spike in the need for their services, with waiting lists growing at many practices and treatment centers across the United States.

The National Eating Disorders Association reported a 41 percent increase in messages to its telephone and online help lines in January 2021, compared with January 2020. And in a study of about 1,000 American and Dutch people with eating disorders published last July, more than one-third of subjects reported that they were restricting their diet and increasing “compensatory” behavior like purging and exercise. Among the Americans in the study, 23 percent said they also regularly binge-eat stockpiled food.

“I’m seeing more clients, and I’m getting clients who are sicker when they come to me, because we cannot get them access to a higher level of treatment,” said Whitney Trotter, a registered dietitian and nurse in Memphis who provides one-on-one nutritional counseling for adolescents and adults. She noted that many in-patient treatment centers were fully booked.

Injecting a rabbit at a laboratory in Vladimir, Russia, in December. The vaccine was developed in part as a public health tool, in case the virus begins to spread easily from animals to humans.
Vetandlife.Ru/via Reuters

MOSCOW — Russia’s state veterinary service said on Wednesday that it had become the first regulator in the world to approve a coronavirus vaccine for animals, intended for use on fur farms or for pet cats and dogs.

The agency said it had developed the vaccine for animals in part as a public health tool, lest the virus spread from animals to humans or — in a worst-case scenario — mutate in animals and then spread back to humans in a more virulent form. It could also revive fur farming after infections on mink farms devastated the business last year, it said.

The agency, the Federal Service for Veterinary and Phytosanitary Supervision, said it did not recommend routine vaccination of animals, for now. The World Health Organization has found no instances of infections in humans caused by pets, the agency said. Though cats and dogs do rarely catch the coronavirus, neither species gets very sick. Lions, tigers and snow leopards can also catch the coronavirus.

The Russian agency noted four reports of pet infections just in the last week, in Italy and in Mexico. It that said a vaccine for pets was needed as insurance against variants that might spread more easily.

“We did this work for the future,” the agency’s deputy director, Konstantin Savenkov, said in a statement. “We should be prepared to prevent a situation rather than deal with it later if it takes a negative turn.”

The vaccine, called Karnivak-Kov, is intended for carnivores. The agency said it had carried out clinical trials on arctic foxes, cats, dogs, mink and other animals. The agency said it would begin industrial-scale production in Russia at a plant that manufactures veterinary drugs.

Fur farmers in Russia, as well as in Austria, Canada, Greece, Poland and the United States, have inquired about buying the vaccine, the agency said. The statement did not say when or if the vaccine would become available for pets.

The problem of animal infections came into focus last year when mink farms culled millions of the creatures because of infection.

Denmark killed all farmed mink — some 17 million animals — after the virus spread from a mink to a human. Separately, a farmed mink in Utah seemed to have passed the virus to at least one wild mink. Scientists have raised alarms about the virus establishing a “reservoir” in wild animals that could later spread back to people.

Russia last August also claimed to be the first country to approve a human vaccine, Sputnik V, though other candidates were in fact further along in clinical trials at the time. It has since promoted Sputnik V to countries around the world, bolstering the Kremlin’s soft power.

A main shopping street in Istanbul last week. On Wednesday, Turkey recorded its highest single-day total of new infections since the pandemic began.
Emrah Gurel/Associated Press

With coronavirus infections surging and the Muslim holy month of Ramadan approaching, the Turkish government is reimposing strict social-distancing measures, including a prohibition on the large gatherings for meals before sunrise and after sunset that are traditional during Ramadan.

Turkey recorded 37,303 new coronavirus cases on Wednesday, the country’s highest single-day total since the pandemic began and a fourfold increase since the beginning of March.

The sharp surge in infections — mostly from the highly contagious variant of the virus that was first identified in Britain — prompted President Recep Tayyip Erdogan to reinstate some of the restrictions he had eased just a few weeks ago.

With nearly two-thirds of adult intensive care beds occupied, the government has ordered restaurants to shift to takeout only and nearly the entire nation of 83 million is being ordered to stay at home on weekends.

In an address to the nation on Monday, Mr. Erdogan said that 80 percent of cities in Turkey were now considered at very high risk for the coronavirus, forcing his government to reinstate lockdown measures.

“The increase in the number of cases and patients, and deaths, obliged us to review the current practices,” he said.

But Mr. Erdogan has come under fire from opposition politicians and Turkish citizens for holding meetings of his governing party in crowded sports complexes around the country, ignoring the social distancing rules that were otherwise strictly enforced by his government. Critics also say that the authorities were too quick to begin relaxing restrictions in early March.

The new lockdowns are expected to be especially difficult for traders and small-business people, who had been hoping for an economic lift during Ramadan.

“The ones meeting at crowded congress are playing with our bread,” tweeted a group that represents cafe, bar and restaurant employees. “The whole sector is getting shut down because of the words coming from the mouth of one single person.”

Even Turkey’s health minister, Fahrettin Koca, appeared to offer veiled criticism of Mr. Erdogan, telling reporters at Parliament on Tuesday that because the virus continues to afflict Turkey, “everyone in this struggle should fulfill their own responsibility.”

Mr. Koca said that Turkey’s vaccination drive would soon gather pace with the delivery of millions more doses of the vaccine produced by the Chinese company Sinovac as well as the Pfizer-BioNTech vaccine. Since January, 6.8 million people in the country have received two doses of the Sinovac shots.

A vaccine center in Munich in December. So far, only about 11 percent of the European Union’s population has received at least one dose.
Laetitia Vancon for The New York Times

The European Union, facing criticism for the slow rollout of vaccines even as waves of infection prompt new lockdowns across the bloc, said that it will have distributed a total of about 107 million doses by the end of March and vowed to speed up distribution.

The goal, according to Dana Spinant, a spokeswoman for the European Commission, was to have enough doses to cover 70 percent of the European Union’s population by July. The commission, which is the bloc’s executive arm and is responsible for ordering the vaccines, said it was expecting 360 million further doses to be delivered before the summer.

So far, only about 11 percent of the bloc’s population has received at least one vaccine shot, compared to 46 percent in Britain and 29 percent in the United States. That has created frustration across the European Union, a feeling that has been exacerbated by the wave of new outbreaks.

Among the roughly 107 million doses, 67.5 million are from Pfizer-BioNTech, 9.8 million from Moderna, and 29.8 million from AstraZeneca. The AstraZeneca figure is a significant decline from the initial commitment by the company to deliver more than 100 million shots in the first three months of the year.

Cuts in supply announced by AstraZeneca have led to a bitter spat between the bloc and the company, significantly slowing down the European Union’s pace of inoculations.

But the headaches with the rollout stem not only from the supply shocks, but also from problems organizing the shots, which is the responsibility of national governments.

Even in richer countries, such as France and Germany, inoculations have been hampered by logistical failures. The temporary halt in use of the AstraZeneca vaccine by many European countries over reports of rare side effects this month also contributed to the slackening of the pace.

The announcement by the European Commission lifted hopes of an improvement in the rollout that could rescue the summer vacation season, which is particularly crucial for the economies of southern European countries, such as Greece, Italy and Spain.

Dolores Hiwiller meeting with her daughters Karen King, right, and Sue Shirey in person for the first time since March of last year.
Kristian Thacker for The New York Times

Every day for a year, Kathy James peered through the window at her mother’s assisted living facility outside Chicago and dreamed of the day they would be together again.

That moment finally came one recent morning, when Ms. James packed a goody bag full of family photographs, a Sunday copy of The Chicago Tribune and a container of potato soup, and met her mother, Renee Koerber, 90, inside the nursing home.

“I said, ‘Mom, we’re in the same room!’” said Ms. James, 63, her heart swelling with relief.

They had made it.

But sitting several feet apart in a common area, where they were not allowed to hug, Ms. James was also startled at how frail her mother looked. She seemed to grow tired after just 15 minutes. “I thought I would be so happy,” Ms. James said. “And I just feel such grief because of the year of time I have lost and I will never get back.”

Many American nursing homes have begun to welcome visitors again after a year of excruciating lockdowns. The Biden administration in March published sweeping guidelines allowing indoor visits in most cases. It is a profound change that comes as vaccinations ramp up, reaching nearly 100 million Americans, including a majority of people in nursing homes.

Even as the head of the Centers for Disease Control and Prevention warned this week of a possible fourth coronavirus surge, nursing homes are so far holding steady, reporting drastically fewer cases and deaths since the start of vaccinations. The improved outlook means that across the country, people are once again greeting loved ones in nursing homes with bouquets of flowers, with homemade pudding and lemon bars, with news from children and grandchildren.

Nursing homes have been centers of the pandemic since the beginning, when an outbreak was first identified at a facility outside Seattle. In the United States, the pandemic has killed more than 179,000 residents and employees of long-term care facilities — one-third of all coronavirus deaths nationwide — and left many others withering in isolation.

In reopening to visitors, nursing homes now offer an early glimpse at what everyone may face in trying to go back to normal after a year of separation and stillness. Some reunions may be tinged with grief, others with reminders of all that has changed.

Pauline Boss, a family therapist and professor emeritus at the University of Minnesota, said the experiences of families coming back together reminded her of research she had done on husbands returning home to wives after war, or cancer patients who suddenly learn they are in remission.

“Things don’t quite get back to normal,” Dr. Boss said.

A Pfizer-BioNTech vaccine is prepared at the Waldron Health Centre in London, England, in January.
Andrew Testa for The New York Times

In January, Britain made a change to its vaccine guidelines that shocked many health experts: If the second dose of one vaccine wasn’t available, patients could be given a different one.

The new rule was based on sheer guesswork. There was no scientific data at the time demonstrating that mixing two coronavirus vaccines was safe and effective. But that may change soon.

In February, researchers at the University of Oxford began a trial in which volunteers received a dose of the Pfizer-BioNTech vaccine followed by a dose of AstraZeneca’s formulation, or vice versa. This month, the researchers will start analyzing the blood of the subjects to see how well the mix-and-match approach works.

As growing numbers of vaccines are being authorized, researchers are testing other combinations. A few are in clinical trials, while others are being tested in animals for now.

Mixing vaccines might do more than just help overcome supply bottlenecks. Some researchers suspect that a pair of different vaccines might work better than two doses of the same one.

“I think we’re on the cusp of some interesting data,” said Adam Wheatley, an immunologist at the University of Melbourne in Australia.

The concept of mixing vaccines — sometimes called a heterologous prime-boost — is not new to our pandemic era. For decades, researchers have investigated the approach, hoping to find potent combinations against a range of viruses, such as influenza, H.I.V. and Ebola.

But scientists had little to show for all that research. It was easy enough to demonstrate that two vaccines may work well together in a mouse. But running full-blown clinical trials on a combination of vaccines is a tall order.

Some researchers are investigating heterologous vaccines not to find a superior mixture, but simply to open up more options for countries desperate to vaccinate their populations. Last week, India held back exports of vaccines to other countries as it grappled with a Covid surge. For countries that were counting on those vaccines, a safe alternative for second doses could save lives.

Worldwide, 13 vaccines are now in use against Covid-19, with 67 more in clinical trials.

“In the current situation, we have a quite a luxurious position of having so many advanced, effective vaccines,” Dr. Wheatley said.

As the number of authorized vaccines grows, the possible combinations in which they can be used will explode.

Whether scientists carry out more experiments on other vaccines will depend on the willingness of the vaccine manufacturers. “You’re requiring quite large pharmaceutical companies to play nice together,” Dr. Wheatley said.

Dr. Bernard Moss, a virologist at the National Institute of Allergy and Infectious Diseases, suspects that a number of companies will be willing to let their vaccines be tested in combinations. “It’s always better to be a part of something that is going to be used,” he said, “than to wholly own something that isn’t.”

Administering the AstraZeneca vaccine in Lviv, Ukraine, this month. Recent opinion polls have shown that about 40 percent of Ukrainians do not trust the shot.
Pavlo Palamarchuk/Reuters

What does it take to get a vaccine in Ukraine? For some people, lots of Facebook friends.

Ukraine’s vaccine effort, which has been among the slowest in Europe, has been hampered by widespread hesitancy, mainly among older people who currently qualify for the shot. The problems have not been helped by the flood of often confusing and bad news around the AstraZeneca vaccine, the main option available in the country. Recent opinion polls have shown that about 40 percent of Ukrainians do not trust the shot.

To bolster acceptance, the Ministry of Health has opened vaccination to people deemed to have a public persona, regardless of their age. That includes actors, pop stars, athletes, writers, journalists — and social media influencers.

The criteria are decided locally, by city officials or doctors at vaccination sites. Those who think they have sway with the public can fill out an online form, which asks how many social media followers they have, on Facebook or on other platforms. Influencers only qualify for shots leftover at the end of the day that might otherwise be wasted.

The main requirement under the program is that recipients share their vaccination selfies on social media.

The program has drawn some bona fide opinion leaders. The Ministry of Health organized a public vaccination of leaders of different religions, for example. “The Lord sent us vaccinations,” the chief rabbi of Kyiv, Jonathan Markovitch, said, encouraging inoculation. “You definitely need to take advantage of this.”

The program was quickly flooded with young influencers. There they were, in glowing good health and at relatively little risk from the disease, posting pictures of themselves getting the shot, grinning or giving a thumbs up.

Some had fewer than a thousand followers on social media. Medical ethicists say that anybody offered a shot should take it, even if they think others may be more qualified. The recipients do not set the rules, after all, and refusing a shot can risk vaccine being wasted.

In the month since Ukraine received its first shipment of 500,000 doses, fewer than half have been administered. The country is going through a new wave of infection, registering this month the highest numbers of new cases and deaths since the beginning of the pandemic.

Still, the ministry published a revised rule this month limiting the program to influencers older than 60, though few could be found.

Jill Biden, the first lady, delivered remarks for César Chávez Day, a holiday honoring the labor organizer.
Pool photo by Anna Moneymaker

DELANO, Calif. — Jill Biden, the first lady, traveled to California on Wednesday to visit a pop-up vaccination site for farmworkers who have lobbied for priority access to shots amid the pandemic.

She told them that their work — and their health — had been essential to a nation crippled by the virus.

“We depended on those who kept going to work every single day,” Dr. Biden told a crowd of about 100 farm workers who had gathered to mark the birthday of César Chávez, the labor organizer who formed the country’s first successful farmworker’s union. “Without the farmworkers who kept harvesting our food, or the factory workers who packaged it, the grocery store clerks who stocked shelves, no one would have made it through this year.”

When she arrived at the “Forty Acres” property just west of Delano, a National Historic Landmark that became the headquarters of the United Farm Workers of America, the first lady was greeted by several members of Mr. Chávez’s family.

Dr. Biden heard from a group of women farmworkers who picked grapes and blueberries in nearby fields. They asked the Biden administration to provide pathways to citizenship, protection from discrimination, and stronger union representation. “We’re a union couple,” Dr. Biden replied.

At one point, the first lady heard from a 27-year-old mother of three that some women were forced to bring their babies and young children to the fields because they did not have access to child care. The first lady told the woman that she hoped some money from the $1.9 trillion stimulus package would reach those workers, but the woman replied that many were undocumented.

In a sign of the labor movement’s significance to the Biden administration, a member of the Chávez family had traveled with her from Washington: Julie C. Rodriguez, the White House’s director of intergovernmental affairs, is Mr. Chávez’s granddaughter.

During her remarks, Dr. Biden said that President Biden supported the Farm Workforce Modernization Act, a bill that would grant temporary legal status to seasonal farm workers, many of whom are undocumented, and offer a 10-year path to citizenship.

“As president, Joe is fighting for people who often go unseen,” Dr. Biden said. “And that’s exactly the kind of immigration policy he’s working to build — one that treats children and families with dignity and creates fair pathways to citizenship, including for essential workers.”

Thousands of Central Valley farmworkers are scheduled to receive the coronavirus vaccine at Forty Acres over six weekends in March and April. Gov. Gavin Newsom of California, a Democrat, and his partner, Jennifer Siebel Newsom, joined the first lady at the site.

Earlier this year, California kicked off a landmark effort to get vaccines to farmworkers, many of whom are undocumented and whose close-quarter working conditions have left them particularly vulnerable to the virus. Researchers from Purdue University estimate that about 500,000 agricultural workers have tested positive for the virus and at least 9,000 have died from it. The virus has killed over 550,000 people in the United States, according to a New York Times count.

Over the course of Mr. Biden’s first two months in office, union leaders have praised his administration as one of the most labor-friendly in modern history. One of Mr. Biden’s first official acts was to move a bust of Mr. Chávez into the Oval Office, a decision Dr. Biden pointed out to applause at the event. Dr. Biden also frequently repeated the farmworker union’s motto, “Sí, se puede,” (“Yes, we can”) several times during the course of her speech.

“César dared to believe that our country could change — that we could change it,” Dr. Biden said. “Now, it’s on us to live up to that promise.”

Hospital workers transferred bodies to refrigerated trucks serving as temporary morgues at Wyckoff Heights Medical Center in Brooklyn in April last year.
Victor J. Blue for The New York Times

Covid-19 was the third leading cause of death in the United States in 2020, displacing unintentional injuries and trailing only heart disease and cancer, federal health researchers reported on Wednesday.

The coronavirus was the cause of death for 345,323 Americans in a year that exacted a steep price in lives lost. In roughly 30,000 additional cases, death certificates cited Covid-19 but it was not deemed the cause of death, according to the National Center for Health Statistics.

Some 3,358,814 Americans died of all causes in 2020, a 15 percent increase in the age-adjusted death rate over that in 2019, when 2,854,838 Americans died. In addition to Covid-19, heart disease claimed higher numbers of lives than expected last year, as did Alzheimer’s and diabetes — a phenomenon statisticians refer to as excess deaths.

“There’s a substantial number of excess deaths, beyond what we would have expected in a normal year,” said Robert Anderson, chief of the mortality statistics branch at the N.C.H.S. and a senior author of two reports published by the Centers for Disease Control and Prevention.

While deaths from heart disease and other illnesses should have increased slightly because of the aging of the population, “this is way up and beyond what we would expect,” Dr. Anderson added.

In a second report issued Wednesday, he and his colleagues scrutinized 378,000 death certificates in 2020 that listed Covid-19 as a factor to determine whether too many deaths had been erroneously attributed to the coronavirus. In the early days of the pandemic, testing was sporadic and patients often died of what initially seemed unrelated causes, like heart attacks.

But the researchers found that the virus was in fact the underlying cause of death in the vast majority of the cases. “Since the beginning of the pandemic, people were claiming deaths were simply being attributed to Covid when people were dying of other causes,” Dr. Anderson said. “We show that’s not the case.”

The researchers’ examination of accompanying conditions on death certificates, like pneumonia or respiratory failure, and contributing conditions, like high blood pressure and diabetes, were consistent with what doctors see in patients who die of Covid-19.

Covid-19 death rates were highest among men; elderly people aged 85 and over; and Native American, Alaska Native and Hispanic individuals. Over all, the highest age-adjusted death rates for all causes were seen among the elderly; Black, Native American or Alaska Native individuals; and men.

A new initiative will make rapid at-home antigen tests available to everyone in two American communities — an important step in determining whether such testing can slow the spread of the coronavirus.
Agence France-Presse — Getty Images

The Centers for Disease Control and Prevention and the National Institutes of Health announced a new initiative on Wednesday to help determine whether frequent, widespread use of rapid coronavirus tests slows the spread of the virus.

The program will make rapid at-home antigen tests freely available to every resident of two communities, Pitt County, N.C., and Hamilton County, Tenn., enough for a total of 160,000 people to test themselves for the coronavirus three times a week for a month.

“This effort is precisely what I and others have been calling for nearly a year — widespread, accessible rapid tests to help curb transmission,” said Michael Mina, an epidemiologist at Harvard University who has been a vocal proponent of rapid, at-home testing programs.

He added, “Taking 30 seconds out of your day three times a week to perform the test is something any person can do.”

Antigen tests are cheaper and faster than P.C.R. tests, which are the gold standard for diagnosing Covid-19, the disease caused by the virus, but they are less sensitive and more prone to false negatives. Mathematical models have suggested that if these tests are used frequently, they can still reduce transmission of the virus.

The tests can help identify people who may not realize that they are infectious, prompting them to self-isolate before they are able to transmit the virus to others. But real world data has been limited, and with virus case numbers still high across the country, testing remains essential, public health experts say.

“We have all hypothesized that testing at home, at scale could stop the chain of transmission of the virus and allow communities to discover many more cases,” said Bruce Tromberg, who directs the National Institute of Biomedical Imaging and Bioengineering and leads its rapid acceleration of diagnostics program, which is supplying the tests for the initiative. “All the mathematical models predict that. But this is a real world, real life example.”

Residents who decide to participate in the program can have the tests delivered to their homes or pick them up at local distribution sites. An online tool will guide participants through the testing process and help them interpret their results. Residents can also volunteer to complete surveys that will assess whether frequent testing has changed their behavior, knowledge about Covid-19, or opinions on vaccination.

Researchers at the University of North Carolina and Duke University will compare the test positivity, case and hospitalization rates in these two communities to those in other similar communities that are not participating in the program.

A. David Paltiel, a professor of health policy and management at Yale School of Public Health, called the launching of a real-world study of the effectiveness of rapid, at-home screening “just great news.” But he cautioned that the results will need to be interpreted carefully, especially if the residents who choose to participate in the initiative are not representative of the community at large.

“We know that self-selection tends to bring out the worried well and a disproportionate number of people who are already Covid-conscious or Covid-conscientious,” he said.

“It’ll be great to see how it works when in the hands of people who really care,” he added. But, he said, the results may not be widely generally applicable to screening programs in which participation is mandatory, as may be the case with some workplace and school programs.