Covid-19: Testing Declines May Be Masking Real Spread of Virus in Parts of U.S.

Declines in coronavirus testing in many states in the South and the Great Plains are making it harder to know just how widely the virus may be spreading in those states, even as restrictions are lifted and residents ease back into daily life, experts say.

States in both regions are reporting few new cases relative to their population, compared with harder-hit states like Michigan or New York. But they are also testing far fewer people.

Kansas, for example, is now testing about 60 people a day for every 100,000 in population, according to data compiled by Johns Hopkins University, and Alabama only a bit more. The picture is similar in Iowa, Mississippi and elsewhere.

By contrast, New York is averaging 1,200 tests a day per 100,000, and Rhode Island 1,677 per 100,000.

Testing has been falling in Kansas since Jan. 1, even though hospitalizations were at their highest level of the pandemic then, according to Tami Gurley, co-chair of the virus task force at the University of Kansas Medical Center. The state is now doing fewer tests relative to its population than any state except Idaho.

The tests they are doing in these low-rate states are finding virus.

Twelve percent of Kansas’ coronavirus tests are coming back positive. Alabama’s positivity rate is 12.8 percent. The rate in Idaho is 27.3 percent, highest in the country. In New York, it’s just 3.5 percent.

So in the states that are doing relatively little testing, it’s possible that their daily case counts are low in part because asymptomatic or mild-symptom cases are going undetected.

Ms. Gurley says she is closely following hospitalizations, as a better indicator of the spread of the virus than new-case reports.

“We think that people are more focused on getting vaccines than getting tested,” she said. “It certainly makes it harder to figure out where we are going. We feel like we are at the point of another uptick in cases.”

Many states in the South and Midwest have relaxed their restrictions, including mask mandates, even though the national data signals that another surge in cases may be coming, according to Edward Trapido, an epidemiologist and associate dean for research at the Louisiana State University School of Public Health.

And many states are shifting resources away from testing to boost vaccination efforts and meet President Biden’s goal of making all adult Americans eligible for a shot by May 1.

As a result, Dr. Trapido said, in many places these days, only the sickest patients are seeking out a coronavirus test.

“As vaccines have become widespread, people are becoming comfortable about not being tested,” he said. “There is a natural experiment going on. It’s a battle between getting people vaccinated and keeping the percent positive low. When I see a slight change in the curve upward, I get alarmed.”

Ms. Gurley said the shift in emphasis away from testing and toward vaccination may stem in part from widespread public fatigue with pandemic precautions and the political imperative in many states to reopen swiftly.

If all you want to do is prevent deaths from the virus, that may make sense, she said, but “if your end goal is to prevent spread, then we need more testing.”

Federal regulators announced Thursday night that they had authorized Moderna to put 50 percent more coronavirus vaccine into its vials, a decision that is expected to boost the nation’s vaccine stock.

The decision provides new assurance of Moderna’s supply and could speed up its deliveries. Like Pfizer, another manufacturer of a two-dose vaccine, Moderna has pledged to deliver a total of 200 million doses by the end of May and 300 million by the end of July.

Moderna had already begun producing fuller vials in anticipation of the Food and Drug Administration’s decision.

The agency told Moderna six weeks ago that it favored increasing the amount of vaccine in vials that it had previously authorized for 10 doses. In a statement, the company said it expects to begin shipping 15-dose vials within weeks.

The F.D.A.’s ruling comes one day after revelations of a setback to the Biden administration’s vaccine rollout. A factory mix-up ruined up to 15 million doses of Johnson & Johnson’s one-shot vaccine, and has delayed F.D.A. authorization of the Baltimore plant where that vaccine is being manufactured.

Although Johnson & Johnson has said it will still be able to deliver 24 million doses this month, as promised, all shipments from that plant have been delayed while the F.D.A. investigates the incident and decides whether to certify production lines there.

Federal officials have been counting on Johnson & Johnson to round out the nation’s vaccine supply. President Biden has promised enough doses for all the nation’s adults by the end of May.

F.D.A. regulators also decided to allow health practitioners to administer an 11th dose of Moderna’s vaccine if they are able to extract it out of vials were previously designated for only 10 doses.

But the agency noted that unless practitioners use specialized syringes and needles, they may might not to be able to extract that 11th dose. They may also be limited to only 13 shots from Moderna’s 15-dose vials.

Those specialized syringes have been in short supply for months.

Moderna was able to quickly modify one or more of its production lines because while it poured more liquid into the vials, the size of vials themselves remained the same. All three of the nation’s federally authorized vaccine manufacturers have been able to produce more vaccine substance than they have been able to bottle in the so-called fill-and-finish phase.

In its statement, Moderna said fuller vials was a way to relieve that bottleneck and accelerate production.

The mishap with Johnson & Johnson’s vaccine occurred at a Baltimore plant run by Emergent BioSolutions, a subcontractor. Workers there accidentally contaminated Johnson & Johnson’s doses with an ingredient used to produce a different vaccine developed by AstraZeneca. AstraZeneca’s vaccine has not been authorized for distribution in the United States. Emergent manufactures both vaccines at the same plant.

Federal officials attributed the mistake to human error. On Thursday, Emergent executives told employees that the entire lot of vaccine substance — the equivalent of up to 15 million doses — would be discarded.

Emergent issued a statement Thursday saying, “Discarding a batch of bulk drug substance, while disappointing, does occasionally happen during vaccine manufacturing.” The company said the error had been detected through “rigorous quality checks.”

American air travel has been picking up, but it is the small, regional, vacation-destination airports that are thriving a little more than a year after the pandemic, while large hub airports have just a fraction of the travelers they did at this time last year, detailed new data shows.

Big-city airports, including those in San Francisco, Portland and Seattle are serving between 24 percent and 46 percent of their typical traveler volume. Washington National, close to the District of Columbia, is down 70 percent in passenger volume, and Kennedy Airport in New York is serving about one-third of its normal volume, according to data from the Transportation Security Administration analyzed by Kevin Williams, a Yale economist who studies air travel.

Smaller regional airports, including those near Jackson Hole, Wyo., and Colorado ski country, have passenger volume as much as 12 percent higher than this time last year. And these airports appear to fall into two categories: those especially close to outdoor vacation destinations, and those serving communities whose residents are more willing to travel amid a pandemic.

The Centers for Disease Control and Prevention continues to advise that people refrain from widespread travel for the time being, while the agency works on travel guidance.

The current guidance addresses local gatherings where fully vaccinated people — now about 16 percent of the total U.S. population — return to some activities in small private settings with other fully vaccinated people, or a fully vaccinated household with one other unvaccinated household. Fully vaccinated people, the agency said, should keep following health and safety precautions in public, including wearing a mask.

But with millions of Americans getting vaccinated each day, and many states rolling back 2020-era restrictions, the drive to return to somewhat normal lifestyles is growing.

Already, some destinations, cruise lines and venues are requiring travelers to provide a C.D.C. vaccination card as proof that they have been inoculated against Covid-19. And there is great interest in a “vaccine passport” that would make vaccination status easy to share digitally.

The Biden administration has stayed clear of such initiatives, leaving the matter to the private sector instead.

“What’s important to us — and we’re leading an interagency process right now to go through these details — are that some important criteria be met with these credentials,” including equitable access and privacy and security concerns, Andy Slavitt, the acting director for the Centers for Medicare and Medicaid Services, said recently.

An updated analysis of clinical trial data shows that the Pfizer-BioNTech coronavirus vaccine continues to offer strong protection without serious safety concerns, the companies said on Thursday.

The new data also suggested that the vaccine works against a worrisome virus variant in South Africa, although more studies are needed, experts said.

Pfizer and BioNTech made the announcement in a news release. The data have not been peer-reviewed nor published in a scientific journal.

Dr. Albert Bourla, Pfizer’s chief executive, said in a statement that the new data “confirm the favorable efficacy and safety profile of the vaccine” and will allow the companies to submit an application to the Food and Drug Administration for full approval. At the moment, the vaccine has received only an emergency authorization from the agency.

The new analysis is an update to data gathered in the more than 44,000-person clinical trial that led to the authorization in the United States and in other countries in December. Pfizer and BioNTech have now recorded 927 cases of Covid-19 among participants in the study, and the new analysis finds that the vaccine is more than 91 percent effective after the second dose, given three weeks after the first.

In November, the companies said that the vaccine was 95 percent effective, a figure based on some 170 Covid-19 cases reported among participants. The new analysis found the vaccine was nearly 100 percent effective in preventing severe disease and death, as was the case in November.

More than 12,000 people who received the vaccine in the trial have passed the six-month mark since the second dose, and no new safety issues were identified, company researchers also said. The companies did not provide specific efficacy data for that group.

A virus variant first identified in South Africa has particularly worried scientists, because it carries mutations that could prevent vaccines from working as well as they do against the original coronavirus. Trials of other vaccines in South Africa, such as those developed by Johnson & Johnson and AstraZeneca, have shown that they are less effective against the so-called B.1.351 variant circulating there.

Pfizer and BioNTech said that among 800 trial participants in South Africa, all nine of the observed Covid-19 cases occurred in those who had received a placebo. Six were infected with the B.1.351 variant, suggesting that the vaccine had worked successfully to block that virus.

The companies have already announced plans to test the effectiveness of a third shot, and are also beginning a clinical trial of a new version of the vaccine that was developed specifically to target B.1.351. Moderna — which, like Pfizer and BioNTech, makes a vaccine based on the mRNA platform — and other companies have announced similar plans.

Natalie Dean, a biostatistician at the University of Florida, said the small number of cases in South Africa made it difficult to interpret the results. And she noted that in the United States, where variants are not yet as widespread, the new analysis concluded that the Pfizer-BioNTech vaccine was nearly 93 percent efficacious, compared to the initial estimate of 95 percent in November.

Dr. Dean said that she would need to see more details of the analysis to make any firm conclusions about that discrepancy. “Some wiggle is expected in the final estimate, so I don’t want to overstate this change,” she said.

Pfizer and BioNTech declined to provide further details.

On Wednesday, the companies reported that a clinical trial had shown their coronavirus vaccine was almost 100 percent effective in adolescents aged 12 to 15, and caused no serious side effects. That data, too, has not yet been peer-reviewed nor published in a journal.

The Biden administration announced an advertising campaign on Thursday intended to encourage as many Americans as possible to be inoculated against the coronavirus, as deep skepticism about the vaccine remains.

The campaign, to air this month on network and cable television and online, comes as the country is moving to rapidly vaccinate Americans and as federal health officials warn against a possible fourth surge of the virus. The average number of new cases reported daily has risen about 17 percent across the country, compared with two weeks ago, according to a New York Times database.

Making equity a focus of its pandemic response, the Biden administration has added mass vaccination sites in several underserved communities. A recent survey conducted by the Kaiser Family Foundation found that the number of Americans, particularly Black adults, who want to get vaccinated has continued to increase. But it also found that vaccine skepticism remains stubbornly persistent, particularly among Republicans and white evangelical Christians. The Biden administration has flagged the issue as an impediment to achieving herd immunity and a return to normal life.

The administration is working with 275 organizations in its new public awareness push — including NASCAR, the Catholic Health Association of the United States and the North American Meat Institute. The advertisements, hopeful in tone and intended as a call to action, are aimed at communities where vaccine hesitancy remains high. For example, many Catholic and evangelical groups are expected to help address religious concerns about the Johnson & Johnson vaccine, which was developed with abortion-derived fetal cell lines.

The group is collectively called the Covid-19 Community Corps, administration officials said, and participating organizations are able to reach millions of Americans who trust them.

“They’re going to listen to your words, more than they are me, as president of the United States,” President Biden said Thursday on a call with faith leaders from around the country.

Administration officials said their research showed that vaccine messaging was often more persuasive coming from medical professionals and community leaders than from celebrities or the president,

The nation was averaging 2.9 million shots a day as of Thursday, according to data reported by the Centers for Disease Control and Prevention. The number has been steadily increasing as more vaccination sites have been set up and more vaccine supply became available.

“We have to be honest that in some communities, there is a concern about getting vaccinated, some based on mistrust based on history, some based on — just rooted in misinformation, of which there is a lot out there,” Vice President Kamala Harris said Thursday during a virtual meeting about educating the public about the vaccines.

While no group is monolithic in its reasons for opposing or accepting the vaccines, the people who say they are skeptical have said they mistrust the government in general and are wary about the vaccine because it was produced quickly. Combating online misinformation remains a challenge; one fast-spreading myth is that tracker microchips are embedded in the shots.

Dr. Anthony S. Fauci, the nation’s leading expert on infectious diseases, explained on Wednesday that the speed in developing the virus vaccines was not a sign of rushed work.

“The speed is really a reflection of decades of scientific advances that led to our being able to make a vaccine and test it so quickly,” Dr. Fauci said during an interview with LL Cool J. “It’s been tested in tens and tens of thousands of people and it has shown a high degree of efficacy and a very, very good safety profile.”

The Department of Health and Human Services has separately bought millions of dollars worth of advertising in Black and Spanish-language media, as well as in outlets that reach Asian-American and tribal communities, reinforcing the message about the safety and efficacy of coronavirus vaccines.

In early March, a New York Times analysis of state-reported race and ethnicity information showed that the vaccination rate for Black people in the United States was half that of white people, and the gap for Hispanic people was even larger. Public health experts have said that obstacles to vaccine access deserve much of the blame for those vaccination disparities.

Black and Hispanic people in the United States are less likely than their white counterparts to have internet access reliable enough to make online appointments; to have work schedules flexible enough to take any available opening; and to have access to dependable transportation to vaccine sites, among other factors. A lack of access to information about the vaccine through trusted providers can also lead to uncertainty and an unwillingness to get a shot.

For rural residents, access to the vaccine is so problematic that they see the logistics and travel time involved as simply not worth it.

Jan Hoffman contributed reporting.

Maine announced on Thursday that adults 16 years and older will be eligible for a vaccine on Wednesday, more than a week sooner than the April 19 deadline the state previously set. Virginia also announced it would allow residents 16 or older to begin getting vaccinated against Covid-19 on April 19, joining more than 40 states that have sped up efforts to open the process to all adults as federal health officials warn about a possible fourth surge of the coronavirus.

“The Covid-19 vaccine is the light at the end of the tunnel,” Gov. Ralph Northam said in a statement. “And that light is getting brighter every day, as more and more Virginians get vaccinated.”

Inoculation efforts in the United States have sped up, as states push to make more adults eligible, heeding a call from the president to rapidly expand eligibility.

Across the country, an average of 2.9 million shots a day were being administered, as of Thursday, according to data reported by the Centers for Disease Control and Prevention. About 32 percent of Virginia’s total population has gotten at least one shot, putting it in the top 20 states, according to a New York Times analysis of C.D.C. data. About 17 percent of Virginia’s total population is fully vaccinated.

Currently, in Maine, about 35 percent of the population have received at least one shot, with 20 percent of the population fully vaccinated.

On Monday, President Biden ordered 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. It builds on his plan for states to open eligibility to all adults by May 1.

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

The announcement by Pfizer and BioNTech this week that a clinical trial found their coronavirus vaccine to be highly effective in adolescents is good news for the 2021-22 school year.

Given the pace of adult vaccinations and the likelihood that they will lead to a decline in cases, many public health experts were already saying that schools should be planning to offer full-time in-person instruction for all grades in the fall.

Still, some teachers’ unions have resisted reopening schools to full capacity, even as teachers are being vaccinated. And many parents — particularly parents of color — have chosen to keep their students in distance learning out of fear about the virus.

Experts say the prospect that children 12 or older will probably have access to vaccines before September should reduce those concerns, and will build pressure on lagging districts to resume in-person instruction. More than anything, it increases the likelihood that middle and high schools will look more like normal in the fall.

Those schools have been more challenging to reopen than elementary schools, for two reasons: Older students are more likely than younger ones to become infected and to transmit the virus, and traditional middle and high school schedules make it difficult to keep students in stable groups.

By some estimates, fewer than half of U.S. high school students attend schools that now offer full-time in-person instruction, and as many as one in five are in schools that are still fully remote.

Dr. Jay Varma, a senior adviser for public health to Mayor Bill de Blasio of New York City, called the clinical trial results from Pfizer and BioNTech “just extraordinary news,” and said, “It may have a really important impact on what happens with school protocols in the fall.”

If many children and adolescents are vaccinated, that will also move the country closer to what scientists call herd immunity, the point at which the virus can no longer spread readily.

That “if” is a big one, though.

Two recent studies, neither of which has yet been peer-reviewed, found substantial vaccine hesitancy among parents of schoolchildren.

In one of the studies, concerns about the vaccine came mostly from mothers, particularly white Republican mothers.

“Amid the spread of both accurate information and politicized disinformation about possible side effects, many mothers feel more capable of controlling the risks of the coronavirus itself than the risks of the coronavirus vaccine,” Jessica Calarco, one of that study’s authors, wrote in an opinion essay in The Washington Post.

Part of the challenge in persuading parents to vaccinate their children is that children rarely experience severe illness from the coronavirus. But experts say that it is critical to vaccinate children to achieve herd immunity and to deter new variants from emerging.

It is unclear whether schools will ultimately add the coronavirus vaccine to the list of vaccinations that students must receive to attend school.

The superintendent of the Los Angeles Unified School District, the country’s second-largest district, said in January that once Covid vaccines were available for children, vaccination would be required for students in classrooms. Unvaccinated students will continued to learn remotely.

But generally it is states, not school districts, that decide which vaccines to require, and some governors have already said they will not make coronavirus vaccines mandatory. Some experts believe that requiring them might backfire, and fuel resistance.

ISLAMABAD — Pakistan said on Thursday that it would allow Covid-19 vaccine doses to be sold commercially to patients, starting with the vaccine developed in China by CanSino Biologics. The Russian Sputnik V vaccine will also be sold, officials said.

The policy will allow affluent Pakistanis to pay to get the shots at large private hospitals whenever they want, while most people wait their turn for a state-supplied vaccination.

“The government will provide free vaccine to 98 percent of the people,” Fawad Chaudhry, the federal minister for science and technology, said on Thursday after a meeting of the federal cabinet in Islamabad. “But 2 percent of the people who don’t want to wait in a line, we have decided to allow the sale of private vaccine.”

The CanSino Biologics vaccine, which is administered in a single shot, will be sold for around $28 a dose, Mr. Chaudhry said.

The pricing for Sputnik V, a two-shot vaccine, is under dispute between the private company that plans to import it and the national drug regulator. Mr. Chaudhry said the company, Ali Gohar Pharmaceutical, wanted a free hand in pricing but the government could not allow that. The company has taken the matter to court in the southern province of Sindh.

On Thursday, Nadeem Akhtar, a judge of the Sindh high court, said in an interim order that “any restriction relating to the sale of the Covid-19 vaccine at this stage would be against the public interest because of the undisputed urgent need due to the crisis currently being faced by the country.” The next hearing of the case is scheduled for April 12.

Pakistan, with a population of more than 220 million, has reported more than 623,000 coronavirus cases and more than 14,000 deaths, according to a New York Times database. Officials said there were 53,127 active Covid cases as of Thursday, and that 98 people had died in the last 24 hours, 29 of whom were on ventilators.

President Arif Alvi; his wife, Samina Alvi; and Pervez Khattak, the defense minister, all tested positive for the virus last week. Prime Minister Imran Khan and his wife, Bushra Bibi, tested positive in March; Mr. Khan has since recovered and resumed his official duties.

The country’s public vaccination program is off to a slow start, in part because the government has not been able to secure large supplies. Officials have said they expect three million doses of the CanSino vaccine to be delivered in the next few weeks.

The government is currently giving doses of another Chinese vaccine, developed by Sinopharm, to people over the age of 60, and began registering people 50 or older for vaccination this week. But according to a major Pakistani news outlet, only about 560,000 people have been inoculated so far, out of the 17 million who are now eligible.

Critics have assailed the slow pace of the free vaccination program, and many opposition politicians and health officials have questioned the government’s decision to allow private sale of the vaccine, raising concerns about affordability and potential corruption.

“The governments all over the world are subsidizing the vaccine for their citizens,” said Faisal Karim Kundi, a spokesman for the opposition Pakistan People’s Party. “The majority of the population is poor in the country. How will the poor afford private vaccination?”

MADRID — In the prelude to Easter, some in Spain are lamenting what they see as a double standard in restrictions to contain Covid-19. The polemic is echoed in other European countries, where the authorities have also tightly restricted domestic travel while allowing their citizens to go abroad and permitting foreign tourists to enter and move about more freely.

The back-and-forth over the rules reflects the difficult balancing acts for European governments trying to blunt the pandemic while keeping their economies afloat, particularly when it comes to the tourism revenues that are so critical to countries like Italy and Spain. After seven years of consecutive growth in tourism arrivals, Spain welcomed 19 million people last year, down from almost 84 million in 2019.

The Spanish government has defended its approach, stressing that visitors from most other countries do not present the same health risks as residents on the move because they must test negative for Covid-19 before traveling. But local residents do not have the option to move around the country, even if they have tested negative, for leisure.

The European Commission, the executive arm of the European Union, introduced plans recently to create a digital certificate that could ease tourism this summer, including internal travel within member states.

“Given that transmission and risk are similar for national and cross-border journeys, member states should ensure there is coherence between the measures applied to the two types of journey,” said Christian Wigand, a commission spokesman.

Opposition politicians in Spain seized on those comments. Some were already accusing the authorities of favoring tourists over residents seeking an Easter getaway.

María Jesús Montero, a minister and spokeswoman for the Spanish government, said last week that the country was doing exactly the same as others in allowing foreign travel but limiting domestic movement.

Italy also has tough rules in place restricting movement across the country. Residents are allowed to leave their town — or their house in the more affected regions — only for work, health reasons or other reasons deemed necessities.

But the government has allowed Italians to travel for tourism to most European countries, including France, Germany and Spain, only asking them to get a negative test 48 hours before their return.

A spokesman for Italy’s health minister said the risk of contagion from international travel with restrictions was lower than that of allowing free movement between domestic regions. One reason for that, he said, is volume — it is easier and cheaper for large numbers of people to travel domestically — adding that it would also be virtually impossible to enforce quarantines on travel between regions.

The Italian hotel association, Federalberghi, was among those accusing the government of double standards.

“Hotels and all the Italian hospitality system have been stuck for months because of the ban on moving from one region to another,” Bernabò Bocca, the president of Federalberghi, said on Sunday. He added, “We do not understand how it is possible to authorize travel across the border and ban it within Italy.”

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.”

ROME — Giulio Macciò tested negative for the coronavirus and spent weeks receiving treatment for emphysema in a sealed-off hospital under the care of doctors and lung specialists — and a nurse who had refused to be vaccinated. On March 11, he unexpectedly died. A post-mortem swab found that he had contracted the virus, as had 14 other patients and the unvaccinated nurse who spent her shifts in his midst.

“It makes no sense that a person whose job is to heal the sick gives them Covid and kills them,” said Mr. Macciò’s son, Massimiliano Macciò, who filed a complaint against the San Martino hospital in the northern Italian city of Genoa where his father was treated. He believes that the nurse, one of an estimated 400 who have refused vaccination against Covid-19 at the hospital, infected his father, who died unvaccinated at 79.

As vaccination rollouts build momentum, businesses everywhere are grappling with whether they can require the inoculation of their employees, raising thorny ethical, constitutional and privacy issues around Europe and the United States. But that quandary becomes all the more urgent when the person is a health care worker.

In Italy, the original Western front in the war against Covid, a rash of outbreaks in hospitals where medical workers have chosen not to be inoculated has raised fears that their stance is endangering public health. It has also prompted a forceful response from an Italian government that is struggling to get vaccinations on track.

On Wednesday, Prime Minister Mario Draghi tested the legal limits of his government’s ability to address the problem by issuing a decree requiring that workers in health care facilities be vaccinated. It also allowed hospital employers to suspend without pay any health care workers who refuse to do so.

Some legal analysts have said that requiring Covid-19 inoculation for health workers could violate Italy’s privacy laws, and that firing or forcing any who decline it to take unpaid leave could be unconstitutional because of a specific article that protects people who refuse health treatments.

Americans have entered a disconcerting phase of the pandemic.

They are awash in hopeful news: With more than 2.8 million shots on average being administered every day, the country is fast approaching universal vaccine eligibility for all adults.

And then there are problems like Michigan.

In a rural stretch of the state along the shore of Lake Huron, coronavirus outbreaks are ripping through churches, schools and restaurants. For more than a week, ambulances have taken several hourlong trips each day to rush Covid-19 patients to I.C.U.s in Detroit, Port Huron or Saginaw.

Even as the pandemic appears to be waning in some parts of the United States, Michigan is in the throes of one of the most alarming outbreaks in the country.

“I never thought we would see this at this time — I thought we would be over the hump,” said Ann Hepfer, a health officer for two counties.

For all the encouraging developments, Americans are getting increasingly ominous warnings about the national picture from public health officials.

On Monday, Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, said she felt a sense of “impending doom” about a potential new surge in cases. President Biden said states should pause their reopening efforts, warning that the country is “giving up hard-fought, hard-won gains.”

Cases, deaths and hospitalizations remain well below the peak levels seen in January. But infection numbers have started rising again, to about 66,000 a day, fueled mostly by pervasive outbreaks on the East Coast and in the Upper Midwest.

The country is a study in contrasts.

Connecticut, New Jersey, New York and other states in the Northeast continue to report high levels of cases, and troubling upticks have emerged in Illinois, Minnesota and some other Midwestern states. But in much of the South and West, case numbers remain relatively low.

California is reporting continued declines, Arizona is averaging about 550 cases a day, down from more than 10,000. And in Arkansas, fewer than 200 cases are being announced most days, down 40 percent in the last two weeks.

But if any place offers a glimpse at the threat of a new surge, it is Michigan.

More than 2,200 coronavirus patients statewide are hospitalized, a figure that has more than doubled since the beginning of March. On Monday, the health system announced that it would reinstate a policy limiting visitors at several hospitals, in response to the latest surge.

Health officials partly attributed the rapid rise in cases to the variant originally identified in Britain, called B.1.1.7, which is widespread in Michigan.

But they have also observed a broader return to prepandemic life seen in a relaxing of mask wearing, social distancing and other strategies meant to slow the spread of the virus — many weeks before a substantial portion of the population is vaccinated.

“It is absolutely alarming,” Emily Toth Martin, an epidemiologist at the University of Michigan School of Public Health, said this week. “Looking at numbers yesterday felt like a gut punch. We’re going to have to go through this surge, and all this hard work again to get the numbers down.”

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.

Despite Hungary’s currently registering one of the highest per capita death tolls in the world, Prime Minister Viktor Orban has said that his government will not tighten restrictions and is determined to continue moving to reopen society.

“Infections are widespread, and lockdowns or curbs can only slow the spread but they can’t stop them,” Mr. Orban said in a televised interview on Wednesday evening.

Mass vaccination, he noted, is the only way to bring the suffering to an end.

After a month of lockdown measures to combat the virus, Mr. Orban said, the plan to reopen stores after Easter, followed by schools and then restaurants and hotels, would not change.

With more than 20 percent of Hungarians having received at least their first dose of a vaccine, the country is ahead of most other European nations. The campaign has been bolstered by Mr. Orban’s decision to import vaccines from China and Russia.

Mr. Orban has sought to keep the focus on the nation’s vaccination campaign, while downplaying the death toll and the impact on the nation’s struggling hospitals.

Hungary registers the highest fatality rate per 100,000 people in the world over the last seven days, according to the New York Times coronavirus database. There were 302 deaths reported on Wednesday, the highest since the start of the pandemic.

Concerned that the Hungarian government was obstructing access to information, more than two dozen mostly internet-based independent news outlets called on the authorities to permit reporters access to hospitals, to allow health care workers to speak with journalists on the record, and to create meaningful engagement between the news media and the government’s coronavirus task force.

The news organizations’ open letter to the government was almost immediately rebuffed by Mr. Orban.

“Now is not the time for us to go into the hospitals to produce bogus videos and fake news,” he said.

But health care experts have argued that the country’s high death rate has been made worse by the broad structural mismanagement of the government response, compounded by the burdens placed on an already understaffed health system.

“We think it’s absurd that doctors and nurses can’t speak about their experiences,” said Peter Peto, editor in chief of 24.hu, an independent Hungarian news site. He added that contrary to what is allowed in other countries, the independent news media in Hungary were not permitted access to hospitals.

“Just as masks and vaccines are key weapons against the coronavirus, so too is the truth,” Mr. Peto said, “And that can only be made available to the public if the media has access to the information and people that deal with Covid.”

LONDON — Paula Smith couldn’t hold back her tears as she faced a sea of hand-painted red hearts covering a wall along the River Thames, each unique, each representing someone who had died of Covid-19 in Britain.

With tears welling, Ms. Smith got back to work painting dozens more hearts on the memorial wall as passers-by stopped to watch. One heart was larger than the others, and on it she wrote in black letters: “Frank Stevens 1941-2020” — a tribute to her 78-year-old father, who died last April.

“Look at how many people we’ve lost,” said Ms. Smith, 49, as she took a step back to look at her work, sobbing behind her protective mask. “We keep talking about numbers, but each heart is a person.”

As European countries have crossed the one-year anniversary of the first coronavirus deaths and lockdown restrictions, memorials have sprung up across the continent to pay tribute to those lost to Covid-19.

The initiative that stretches along the southern bank of the Thames in London may be one of the most significant efforts to date.

Bereaved families have filled a wall 6.5 feet high with thousands of hearts that they say will eventually contain about 150,000, one for every person with Covid-19 marked on a death certificate in Britain. The country has so far recorded just over 149,000 deaths in that category so far. According to a New York Times database, the country’s toll is the largest in Europe and the fifth-highest in the world.

As vaccinations become more widely available for people in the United States and travel starts picking up, many people have started sharing their simple white vaccination cards on social media as prized new possessions.

With some destinations, cruise lines and venues already requiring travelers to provide proof of vaccination against Covid-19, keeping that record is key. Last week, New York became the first state to introduce a digital tool to allow people to easily show that they have either tested negative or been inoculated against the virus in order to gain entry into some events and venues. But until such measures are taken more widely across the country, you’ll want to hang onto that little white card.

Here’s everything you need to know about your vaccine record, why it’s important and how to keep it safe.

What’s on your vaccine card?

The vaccine card, given after your first shot and then updated if your vaccine requires a second one, includes the vaccine manufacturer, the dose numbers and the date and location each was administered, according to Alex Brown, a spokeswoman for Walgreens, which is administering vaccinations at more than 5,000 stores nationwide.

What happens if I lose my card?

Getting a new card is easy enough if you got vaccinated at a pharmacy like Walgreens. Ms. Brown said that anyone who loses their card should return to where they were vaccinated and a pharmacy employee can print out a new card from the patient’s electronic records.

Vaccinations are also tracked by state health departments, so you can reach out to your state’s agency to get a replacement card, according to the Centers for Disease Control and Prevention.

Do I need my card to travel?

Some destinations and cruise lines have started requiring that travelers be fully vaccinated before they travel. As of March 26, fully vaccinated Americans who can present proof of vaccination can visit Iceland, for example, and avoid border measures such as testing and quarantining, the country’s government said.

The cruise line Royal Caribbean is requiring passengers and crew members 18 or older to be vaccinated in order to board its ships, as are Virgin Voyages, Crystal Cruises and others. For the moment, airlines are not requiring vaccinations for travel.

Will the Biden administration require a vaccine passport?

Among the Biden administration’s executive orders aimed at curbing the pandemic is one that asked government agencies to “assess the feasibility” of producing digital versions of vaccination documents. The administration has said that it would not be passing a federal mandate or distributing its own vaccine passport.

In a White House Covid-19 news conference on Monday, Andy Slavitt, the acting director for the Centers for Medicare and Medicaid Services, said that “unlike other parts of the world, the government here is not viewing its role as the place to create a passport, nor a place to hold the data of citizens.”

Hong Kong health officials said on Thursday that they would resume use of the Pfizer-BioNTech coronavirus shots next week amid a continuing investigation by the German manufacturer into packaging defects that were discovered in two batches.

The manufacturer, BioNTech, said it had found no evidence that the defects had compromised the vaccine’s safety. Until the inquiry is completed, however, Hong Kong officials said that they would administer doses from a shipment handled by a different packaging plant in Germany, where defects have not been found after repeated tests.

Constance Chan, Hong Kong’s director of health, said at a news conference that Pfizer-BioNTech vaccinations would resume on Monday, nearly two weeks after the Chinese territory suspended use because of loose lids and leakages that were found in some vials.

The suspension dealt another blow to the inoculation drive in Hong Kong, where only 6 percent of the city’s 7.5 million people have received a first vaccine dose.

About 183,000 residents who had signed up to receive the Pfizer-BioNTech vaccine had their appointments abruptly canceled. Bookings for the other vaccine that Hong Kong is using, manufactured by the Chinese company Sinovac, have fallen in recent weeks after reports that people had died after receiving it. Officials have found no direct link between the shots and the deaths.

Ms. Chan stressed that BioNTech had found no signs that the vaccines administered to residents before the suspension were unsafe. The manufacturer told Hong Kong officials that the freezing temperatures at which the vials of vaccines are stored made bacterial contamination extremely unlikely and added that its inspections had not turned up any other problems.

The company’s analysis showed that the low storage temperatures had decreased the flexibility of the vials’ plastic stoppers, potentially causing looseness around the metal rings at the openings of some of the vials. The resulting increase in air pressure inside the vials could cause spillage. But when the vials are unthawed before use, the plastic stopper regains its flexibility and the vial becomes airtight again, Ms. Chan said.

It was not clear whether such packaging issues could emerge in other places where the vaccine is in use. BioNTech has said that the flaws were limited to two batches that were shipped to Hong Kong and Macau, another Chinese territory, and handled by a Chinese distributor, Fosun Pharma.

In nearly three decades as chief demographer at the Department of City Planning, Joseph J. Salvo has provided data and analysis of the ever-changing populace to help officials, community organizers and journalists understand New York, the most diverse city in the world.

Days before his retirement on Thursday at age 65, Mr. Salvo, shared his predictions for a post-pandemic city. Below are edited excerpts from the conversation.

What are the effects of the coronavirus pandemic and what comes next?

There is so much talk of people leaving the city. There has been temporary dislocation, but I think it’s mostly a phenomenon among people who have the resources to move. If you ask me what the real threat to the city is, I will tell you the real threat is that we stop attracting immigrants.

The city’s population boomed early in the last decade. But, starting in 2016, immigration to the city starts to go down substantially. We are talking about a 46 percent decline in the number of immigrants coming to the city. Half of the births are to immigrant women. So births are down, too. All of this has caused the population to decline. The biggest fear I have with Covid is New York not being a magnet for those people with the greatest aspirations.

Why is that important?

I lived through the 1970s in the city. New York City was in the throes of a major crisis. The city was broke. There were a lot of people who were down on the city and a tremendous loss of population. From 7.9 million people it went all the way down to 7.1 million people in the course of a single decade. At the same time, 800,000 immigrants came to the city. It was true that New York City was in terrible shape, but it also offered a lot of opportunities. The city rose up and prospered, largely on the backs of immigrants. So we have been in this cycle before.

Working-class immigrants were one of the groups hit hardest by the pandemic. Why? And what will that mean for recovery?

In the pandemic, they are trying to make a living and coming home and living in close proximity to other people. And they work the cash-only jobs, service jobs, services in buildings, home health aides, that we start to lose. Our growth is going to depend on giving support to these immigrants, many of whom suffered and lost family members.

What do you think the city should do to support a recovery?

The questions we are looking at today are access to housing, equity and fairness, and those issues need to be tackled head on. Those issues are now on the front burner. Housing is something to watch. People are living in overcrowded housing situations, and I think that’s one of the reasons the crisis was so bad.

What’s the best bet for a recovery?

What we pray will happen is that the city will come back with a ferocity we have never seen in food, beverage, entertainment and hotels. All of that is going to come back. And hopefully the immigrant population will prosper because of that. That’s the key.