Nurses prepared vaccine doses in Munich last month. The Johnson & Johnson vaccine’s rollout was paused in Europe, threatening efforts to increase vaccinations throughout the bloc.
Laetitia Vancon for The New York Times

First it was AstraZeneca. Now Johnson & Johnson.

Last week, British regulators and the European Union’s medical agency said they had established a possible link between AstraZeneca’s Covid-19 vaccine and very rare, though sometimes fatal, blood clots.

On Tuesday, Johnson & Johnson said it would pause the rollout of its vaccine in Europe and the United States over similar concerns.

Regulators have asked vaccine recipients and doctors to be on the lookout for certain symptoms, including severe and persistent headaches and tiny blood spots under the skin. Doctors’ groups have circulated guidance about how to treat the disorder.

The troubles with two major vaccines are casting a cloud over the European Union’s vaccine rollout just as it has finally begun to gain momentum after months of short supplies and logistical problems.

According to a YouGov poll published last month, 61 percent of the French, 55 percent of Germans and 52 percent of Spaniards consider the AstraZeneca vaccine “unsafe.” That is in stark contrast to the findings of a similar poll from February, when more people in those countries, with the exception of France, believed that the shot was more safe than unsafe.

Almost everywhere across the European Union, it seems, many are eager for alternatives, as the new types of vaccines that include the Moderna and Pfizer, which utilize science known as “mRNA,” have not been associated with similar side effects.

Although all E.U. countries have been offered a chunk of each vaccine approved in the bloc so far — AstraZeneca, Johnson & Johnson, Moderna and Pfizer — many opted to forgo parts of their share of more expensive or cumbersome vaccines like Pfizer and Moderna early on, instead favoring the AstraZeneca jab.

“In Britain or Eastern Europe, a big part of the campaigns are based on AstraZeneca,” said Yves Van Laethem, a top epidemiologist who is Belgium’s Covid task force spokesman.

Wealthier bloc members like Denmark, France, Germany and the Netherlands can better compensate for the loss of confidence in AstraZeneca, because they acquired extra doses of other vaccines — especially Pfizer — through a secondary market after poorer E.U. nations gave theirs up.

Those countries — including Bulgaria, Croatia, Latvia and Slovakia — are likely to be less able to quickly offer alternatives.

Raphael Minder contributed reporting from Madrid and Constant Méheut from Paris.

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Jeffrey D. Zients, the White House Covid-19 response coordinator, said Tuesday that pausing the use of Johnson & Johnson’s coronavirus vaccine would not impact the administration’s vaccination goals.Chang W. Lee/The New York Times

Injections of Johnson & Johnson’s single-dose coronavirus vaccine came to a sudden halt in much of the country on Tuesday after federal health agencies called for a pause in the vaccine’s use after discovering a rare blood clotting disorder in six recipients.

All six were women between the ages of 18 and 48 and all developed the illness within one to three weeks after being vaccinated. One woman died and a second woman in Nebraska has been hospitalized in critical condition.

Over seven million people in the United States have received Johnson & Johnson shots so far, and about nine million more doses have been shipped out to the states, according to data from the Centers for Disease Control and Prevention.

“We are recommending a pause in the use of this vaccine out of an abundance of caution,” Dr. Peter Marks, the director of the Food and Drug Administration’s Center for Biologics Evaluation and Research, and Dr. Anne Schuchat, principal deputy director of the C.D.C., said in a joint statement. “Right now, these adverse events appear to be extremely rare.”

While officials framed the move as a recommendation to health practitioners, the impact was immediate. By Tuesday evening, all 50 states, Puerto Rico and Washington, D.C. announced a pause in administration of the vaccine. Ohio’s governor, Mike DeWine, announced that eight mass vaccination sites across his state would shut down for the week.

The federal government temporarily halted administration of the shots by the U.S. military, federally-run sites and CVS and Walgreens, two pharmacy giants that participate in a federal vaccination program, officials said.

Dr. Janet Woodcock, the acting commissioner of the F.D.A., said at a news conference Tuesday that the pause was only expected to last “a matter of days,” although she said the time frame depends on “what we learn in the next few days.” Dr. Schuchat said at the same briefing that the pause was enacted in part to “prepare the health care system to recognize and treat patients appropriately.”

In a statement, Johnson & Johnson said it supported “open communication” with health care professionals and the public and had been working closely with medical experts and health authorities. The company said that it was pausing vaccinations in its clinical trials. It is now testing the effectiveness of two doses, as opposed to the single dose that was authorized in February.

Scientists with the F.D.A. and C.D.C. will jointly examine possible links between the vaccine and the disorder and determine whether the F.D.A. should continue to authorize use of the vaccine for all adults or modify the authorization, possibly limiting it to certain population groups. An emergency meeting of the C.D.C.’s outside vaccine advisory committee has been scheduled for Wednesday.

The move could complicate the nation’s vaccination efforts at a time when many states are confronting a surge in new cases and seeking to address vaccine hesitancy. Regulators in Europe and elsewhere are concerned about a similar issue with another coronavirus vaccine, developed by AstraZeneca and Oxford University researchers, that has not been authorized for emergency use in the United States. At the news conference, Dr. Marks drew a connection between the two vaccines, saying the cases involving rare blood clots were very similar.

The announcement reverberated elsewhere around the world, too. Johnson & Johnson said that it would delay its vaccine rollout in Europe, where several countries were poised to start administering it this week. Australia also announced that it would not purchase any doses.

South Africa temporarily suspended its rollout of the Johnson & Johnson vaccine, a setback for the country. South Africa pivoted to the vaccine in February after it halted use of the AstraZeneca-Oxford shot, after evidence emerged that it did not protect clinical-trial participants from mild or moderate illness caused by the virus variant that is dominant in the country. The Johnson & Johnson vaccine had a 64 percent efficacy rate in South Africa, according to an F.D.A. analysis.

The reaction prompted an intense debate among public health experts about whether guarding against such a rare disorder was worth the cost. Scores of vaccine appointments were canceled this week, and some public health officials feared that by fueling vaccine hesitancy and conspiracy theorists, the pause could prompt fewer Americans to get vaccinated — and expose them to far more risk.

Others said the F.D.A. and the C.D.C. simply had no choice.

“It’s incredibly challenging, but to ignore it would have been worse,” said Rachael Piltch-Loeb, an expert in health risk communication at the N.Y.U. School of Global Public Health. If the public suspected that the government was concealing serious potential side effects, she said, far more people might decide against vaccination.

Jeffrey D. Zients, the White House Covid-19 response coordinator, said Tuesday the pause “will not have a significant impact” on the nation’s vaccination program, and that the administration will still “reach every adult who wants to be vaccinated.”

The vast majority of the U.S. vaccine supply comes from Pfizer-BioNTech and Moderna, and Mr. Zients said people with appointments for Johnson & Johnson shots would be switched to the other two vaccines. “We purchased excess supply so that we’d be ready for any contingency,” he said, adding that the federal government shipped out 28 million doses of the two vaccines this week. As of Monday, the country was averaging over 3.3 million doses a day, according to C.D.C. data.

With the Johnson & Johnson setback, federal officials expect there will only be enough to cover fewer than 230 million adults, roughly 30 million shy of the total adult population. But a certain percentage of adults are expected to refuse shots, despite public campaigns to convince them, so the supply may cover all the demand.

An emergency meeting of the C.D.C.’s outside advisory committee made up of independent experts has been scheduled for Wednesday to discuss how to handle the vaccine in the future.

Eileen Sullivan, Denise Grady, Carl Zimmer, Monika Pronczuk and Lynsey Chutel contributed reporting.

Registered nurse holding a Johnson & Johnson Covid-19 vaccine in Chicago last month.
Kamil Krzaczynski/Agence France-Presse — Getty Images

On Tuesday morning, U.S. federal health regulators recommended a pause in the use of Johnson & Johnson’s Covid-19 vaccine while they investigated six reports of blood clots in women ages 18 to 48. One has died, and a second is hospitalized in critical condition.

Experts have yet to determine to what extent, if any, the vaccine is responsible for the clots. But the investigation follows actions by European regulators who concluded that a vaccine made by AstraZeneca may also be the cause of a similar, extremely rare clotting disorder.

U.S. and European public health experts have emphasized that for most people, the benefits of the Covid vaccines far outweigh the risks.

Here are some of the common questions being asked and what we know so far.

Fewer than one in a million J&J vaccinations are now under investigation. If there is indeed a risk of blood clots from the vaccine — which has yet to be determined — that risk is extremely low. The risk of getting Covid-19 in the United States is far higher.

The F.D.A. recommends that people who have received the Johnson & Johnson vaccine within the past three weeks should contact their doctors if they experience severe headaches, abdominal pain, leg pain or shortness of breath.

Six women in the United States who received the Johnson & Johnson vaccine developed a rare disorder involving blood clots within about two weeks of vaccination. In the condition, called cerebral venous sinus thrombosis, clots form in veins that drain blood from the brain.

Researchers studying a very similar disorder in AstraZeneca recipients in Europe say it appears to be caused by an intense reaction to the vaccine by the immune system, which generates antibodies that activate platelets, a blood component that helps form normal clots to repair wounds. In addition to clots, abnormal bleeding occurs.

Dr. Peter Marks of the F.D.A. said it was the unusual combination of clotting and bleeding that set up a red flag for regulators as a possible safety signal.

At the news conference on Tuesday, Dr. Marks said the cases were “very, very similar.”

Both Johnson & Johnson and AstraZeneca use adenoviruses to carry DNA into human cells to begin the process of generating immunity to the coronavirus. It is not yet known whether that technology causes the problem.

German researchers have speculated that DNA from the vaccine may set off the immune reaction in some people. But the condition is so rare that the researchers say patients likely also have some individual biological trait — as yet unknown — that predisposes them to the immune overreaction.

Doctors in Germany and Norway have treated patients with blood-thinning drugs to try to stop the growth of the clots, and with intravenous immune globulin, which can help eliminate the misguided antibodies that are causing the problem.

Researchers there and U.S. federal health officials on Tuesday advised against using a common blood thinner, heparin, and choosing alternative medicines instead. The reason is that the disorder closely resembles a rare syndrome caused by heparin, and it is possible that heparin could make things worse in these patients.

The F.D.A. has not found any similar cases in people who have received the Moderna or Pfizer-BioNTech vaccines.

Benjamin Mueller contributed reporting.

A Kent State University student getting his Johnson & Johnson vaccination in Kent, Ohio, last week.
Phil Long/Associated Press

Following a call from federal health agencies, all 50 states quickly paused or recommend that providers pause the administration of Johnson & Johnson’s vaccine after six women in the United States developed a rare disorder involving blood clots within one to three weeks of vaccination. Washington, D.C., and Puerto Rico also said they would halt administration of that vaccine.

CVS and Walgreens, the nation’s largest retail pharmacy chains, also said that they would immediately stop Johnson & Johnson vaccinations. Both companies said they were emailing customers whose appointments would be canceled and would reschedule appointments when able. Rite Aid would also be temporarily pausing the administration of the vaccine “out of an abundance of caution,” a spokesman said.

Publix and Wegmans, two sizable U.S. supermarket chains, likewise announced they would be suspending the use of that vaccine. Wegmans said it would cancel all appointments for the Johnson & Johnson vaccine, but would continue to offer the Moderna and Pfizer-BioNTech doses where available, and Publix said that customers could schedule a Moderna vaccine online.

The retail giant Walmart “immediately paused” administration of the Johnson & Johnson vaccine, and will offer customers with existing appointments a different vaccine if it’s available — but would cancel and rebook the appointment for a “later date” if supply is not sufficient, a spokeswoman said.

Gov. Mike DeWine of Ohio and the state’s chief health official said they were advising all state vaccine providers to temporarily halt use of the single-dose vaccine. Later in the day, Mr. DeWine announced that the state’s mass vaccination sites, which were slated to administer Johnson & Johnson shots, would close temporarily because of the pause.

Connecticut health officials said they told vaccine providers to delay planned appointments or give an alternative option if they had the supply. New York’s health commissioner, Dr. Howard Zucker, said the state would stop using the Johnson & Johnson vaccine while the Food and Drug Administration and the Centers for Disease Control and Prevention evaluate the safety risks. Appointments for Johnson & Johnson’s shot on Tuesday at state mass sites would be honored with Pfizer doses, Dr. Zucker said.

California’s top epidemiologist, Dr. Erica Pan, said that the state would follow the federal guidance and was directing health care providers to pause the administration of the vaccine, “until we receive further direction from health and safety experts.”

The pause in California comes before the state is set to expand eligibility to anyone age 16 and older on Thursday — a move that some experts have worried will lead to frustration, as an explosion in demand for doses coincides with a decrease in supply and strains an already-confusing patchwork of appointment systems. Questions loomed about how long the pause would last, as well as whether the slowing of supply would affect the state’s reopening plans.

Gov. Gavin Newsom said on Twitter that the state is vaccinating more than 3 million people per week, and that the state is “still on track to fully reopen” on June 15 — but the plan is dependent on widespread accessibility of vaccines.

The Biden administration on Tuesday insisted that the pause would not disrupt vaccination efforts, which has accelerated in recent weeks as a rise in new virus cases threatens a fourth possible surge. Jeffrey D. Zients, the White House Covid-19 response coordinator, said the government would still have ample doses to cover every adult who wants to be vaccinated by the end of next month. Many states have already opened vaccination eligibility to all adults and others plan to by next week.

As of Monday, 36 percent of the country’s total population has received at least one shot of a vaccine, and 22 percent are fully vaccinated, according to data from the C.D.C.

Even though the reaction to the Johnson & Johnson shot is rare, any questions about the safety of the shots could bolster vaccine hesitancy.

Over seven million people in the United States have received Johnson & Johnson shots so far, and roughly nine million more doses have been shipped out to the states, according to data from the C.D.C. The six women who developed blood clots were between the ages of 18 and 48. One woman died and a second woman in Nebraska has been hospitalized in critical condition.

Scientists with the F.D.A. and C.D.C. will jointly examine possible links between the vaccine and the disorder and determine whether the F.D.A. should continue to authorize use of the vaccine for all adults or limit the authorization. Dr. Anthony S. Fauci, a White House medical adviser, suggested that the vaccine would likely be brought back into play. But “I can’t guarantee it,” he said.

The C.D.C.’s outside advisory committee of independent experts has scheduled an emergency meeting for Wednesday.

Like many states, New York had already prepared for a significant drop in its supply of the Johnson & Johnson vaccine after federal officials said that supplies would be limited because of a production issue at a Baltimore manufacturing plant. On Friday, Gov. Andrew M. Cuomo said that New York expected to receive 34,900 Johnson & Johnson shots, a decrease of 88 percent from the previous week.

Dr. Zucker, New York’s health commissioner, said that the state would honor appointments made at state-run mass vaccination sites for the Johnson & Johnson vaccine by giving people the Pfizer-BioNTech vaccine instead. At an appearance later, Mr. Cuomo said that the state had enough supply of the Pfizer and Moderna vaccines on hand to be able to adhere to its current vaccination pace.

Mayor Bill de Blasio of New York City said that the city would work with its vaccination sites to help people get appointments for the Pfizer or Moderna vaccine instead, rescheduling appointments at city-run vaccine sites.

Both Mr. Cuomo and Mr. de Blasio received the Johnson & Johnson vaccine at separate appearances last month, which they framed as an effort to boost confidence in that vaccine’s efficacy rate and to address vaccine hesitancy.

The city’s health commissioner, Dr. Dave Chokshi, said that about 234,000 residents have received the Johnson & Johnson vaccine and none had reported any blood clots so far. The city had been relying on the vaccine to inoculate hard-to-reach New Yorkers, including people who are homebound.

Regulators in Europe and elsewhere are concerned about a similar issue with another vaccine, developed by AstraZeneca and Oxford University researchers. That vaccine has not been authorized for emergency use in the United States.

Rebecca Robbins, Jill Cowan, Denise Grady, Carl Zimmer and Sharon Otterman contributed reporting.

The Javits Center vaccination site in New York City last month.
James Estrin/The New York Times

A recommendation from federal health agencies to pause the rollout of Johnson & Johnson’s one-dose vaccine over a rare disorder involving blood clots in six recipients has left states like New York in a bind.

Before it was prompted to halt distribution of the Johnson & Johnson vaccine by the announcement, New York had like other states already prepared for a significant drop in its stockpile of the shot after federal officials said that supplies would be limited because of a production issue at a Baltimore manufacturing plant.

On Friday, Gov. Andrew M. Cuomo said that New York expected to receive 34,900 Johnson & Johnson shots, a decrease of 88 percent from the previous week.

Dr. Zucker, New York’s health commissioner, said that the state would honor appointments made at state-run mass vaccination sites for the Johnson & Johnson vaccine by giving people the Pfizer-BioNTech vaccine instead. At an appearance later, Mr. Cuomo said that the state had enough supply of the Pfizer and Moderna vaccines on hand to be able to adhere to its current vaccination pace.

Mayor Bill de Blasio of New York City said that the city would work with its vaccination sites to help people get appointments for the Pfizer or Moderna vaccine instead, rescheduling appointments at city-run vaccine sites.

Both Mr. Cuomo and Mr. de Blasio received the Johnson & Johnson vaccine at separate appearances last month, which they framed as an effort to boost confidence in that vaccine’s efficacy rate and to address vaccine hesitancy.

The city’s health commissioner, Dr. Dave Chokshi, said that about 234,000 residents have received the Johnson & Johnson vaccine and none had reported any blood clots so far. The city had been relying on the vaccine to inoculate hard-to-reach New Yorkers, including people who are homebound.

Roger Fernandez, a pharmacist at Freya Pharmacy, a small drugstore on 39th avenue in the Corona neighborhood of Queens, called the 10 people who were scheduled to receive Johnson & Johnson vaccine’s on Tuesday as soon as they learned about the possible side effects and told them they would reschedule their appointments once the pharmacy received a new shipment of Moderna’s vaccine.

Mr. Fernandez, said that he felt that “it’s too early for anyone to say anything” for certain about the Johnson & Johnson vaccine, but that he was glad that the authorities were being “extra cautious.”

“You have to worry about everything,” he said, since no medications were entirely safe. “We have people that are allergic to penicillin, but we don’t take penicillin out of the market.”

He said that the patients he had spoken to Tuesday were “not really scared” of any of the vaccines, and were eager to come in for the Moderna shot when they arrived.

A box of Johnson & Johnson Covid-19 vaccines shown by a pharmacist in Budapest, Hungary, on Tuesday.
Szilard Koszticsak/EPA, via Shutterstock

Johnson & Johnson on Tuesday said it would delay the rollout of its vaccine in Europe amid concerns over rare blood clots found in recipients in the United States, just as several countries of the bloc were poised to start administering the vaccine later this week.

It was another blow to the continent’s ambition to ramp up inoculation campaigns that have lagged behind other countries in the West. The European Union had expected the vaccine to boost its efforts to vaccinate 70 percent of adults by September.

“The safety and well-being of the people who use our products is our number one priority,” Johnson & Johnson said in a statement when it announced its plans to delay the rollout of the vaccine, adding that it had been reviewing the cases of blood clots detected in the United States with European health authorities.

On Tuesday, United States health officials called for a pause in the use of the Johnson & Johnson single-dose coronavirus vaccine after rare blood clotting was reported in six recipients — women between the ages of 18 and 48 who developed symptoms within one to three weeks of vaccination. One woman died and a second woman has been hospitalized in critical condition. More than 40 states quickly paused or recommend that providers pause administration of the dose.

Over seven million people in the United States have received Johnson & Johnson shots so far, and about nine million more doses have been shipped out to the states, according to data from the Centers for Disease Control and Prevention.

Following the decision in the United States, South Africa also announced it would pause vaccinations, even as the Johnson & Johnson shot is the only one currently offered in the country. So far, the vaccine has been administered to about 290,000 health workers.

The country’s health minister, Dr. Zwelini Mkhize, said the pause was precautionary, and he expected the rollout to resume in a few days after authorities investigated the cases.

“Science must be respected at all times, although this may mean a disruption in our plans,” Mr. Mkhize said on Tuesday. The country has also secured 30 million doses of the Pfizer-BioNTech vaccine, two million of which will arrive by May, the minister said.

In Europe, the first signs of concern came last week when the European Medicines Agency, the bloc’s drug regulator, said it was investigating reports of four cases of blood clots in people who had received a shot of Johnson & Johnson’s Janssen vaccine in the United States, one of them being fatal. The regulator said it wasn’t clear if there was a link between the vaccine and the clots, adding that it treated the reports as “safety signal” that required further assessment.

Johnson & Johnson started delivering its one-shot vaccine to the bloc on Monday, with some member countries like Spain and Belgium already having received modest quantities of the shot, and preparing for the rollout later in the week. Fifty-five million doses of Johnson & Johnson’s vaccine are expected to be delivered to the European Union by the end of June, and another 120 million later in the year, according to Thierry Breton, the bloc’s top industry official.

Europe has been embroiled in a regulatory back-and-forth over another vaccine, AstraZeneca’s. Several countries have restricted the use of the vaccine in younger people, after the European Medicines Agency said there was “a possible link” between blood clots and the vaccine earlier this month, and said it should be listed as a rare side effect.

Both Johnson & Johnson and AstraZeneca use the same technology, prompting concerns that the blood clots reported in recipients of both vaccines could be the same rare, yet sometimes fatal side effect.

The agency stopped short of advising to curb the use of the vaccine in 27 member countries, saying that it was up to the national authorities to decide who should receive which vaccine, which resulted in a patchwork of different national regulations.

France and Belgium have restricted its use for those older than 55, and Germany, Italy and Spain, for those over 60. Some other countries, such as Poland, which rely heavily on AstraZeneca in their national rollouts, decided to go ahead with AstraZeneca’s vaccine.

Eileen Sullivan contributed reporting.

Gigi Lin, right, owner and pharmacist of Corner Chemists Pharmacy in Chinatown, giving the first dose of the Moderna vaccine to Lorraine Rubio in New York on Tuesday.
James Estrin/The New York Times

The Moderna coronavirus vaccine continues to provide strong protection in the United States against Covid-19 six months after vaccination, the company announced Tuesday.

The vaccine, after both doses are given, has been more than 90 percent effective at protecting against Covid-19 and 95 percent effective at protecting against severe disease, the company said in a statement. The results are based on more than 900 total cases of Covid-19, including 100 severe cases, that have been identified in participants of Moderna’s phase three vaccine trial as of April 9.

Pfizer recently announced that its vaccine was more than 90 percent effective against Covid-19 after six months and 95 to 100 percent effective against severe disease. Both companies are now testing their vaccines in children.

It is not yet clear whether the overall effectiveness of the vaccines will drop as dangerous new variants, some of which may evade vaccine-induced antibodies, spread more widely throughout the United States.

Moderna’s results, which “remain preliminary,” the company noted, have not yet been reported in a scientific journal. But they are consistent with results that were published in The New England Journal of Medicine last week. In that report, which is based on 33 adults who had received the Moderna vaccine, researchers found that study participants continued to have high levels of antibodies against the coronavirus six months after their second dose.

The company also announced preliminary results from tests of potential vaccine boosters in mice. One shot is designed to protect against B.1.351, the variant first identified in South Africa. The other combines that more targeted vaccine with the original formulation. Both boosters increased antibody levels in the mice, but the latter seemed to produce the strongest immune response in the mice, the company said, though it did not provide more detailed data.

Students line up for vaccines at Oakland University on Friday in Rochester, Mich. Coronavirus cases in the state have continued to rise in recent weeks.
Emily Elconin for The New York Times

The virus is again surging in parts of the United States, but it’s a picture with dividing lines: ominous figures in the Northeast and Upper Midwest, but largely not in the South.

Experts are unsure what explains the split, which doesn’t correspond to vaccination levels. Some point to warmer weather in the Sun Belt, while others suspect that decreased testing is muddying the virus’s true footprint.

The contours of where the virus is resurgent can be drawn around one figure: states that are averaging about 15 new cases a day for every 100,000 people. The 23 states — including Alabama, Mississippi and Arkansas — that have averaged that or fewer over the past week seem to be keeping cases relatively low, according to a New York Times database.

In the 27 states above that line, though, things have been trending for the worse. Michigan has the highest surge of all, reporting the most drastic increase in cases and hospitalizations in recent weeks. Illinois, Minnesota and others have also reported worrisome increases.

Nationally, reported cases in the United States are growing again after a steep fall from the post-holiday peak in January. In the past two weeks, new confirmed cases have jumped about 11 percent, even though vaccinations picked up considerably, with an average of over 3.3 million doses given daily.

Hospitalizations are rising in some states, most notably in Michigan.

Some Southern states, like Alabama and Mississippi, are lagging in vaccinations. Only about 28 percent of people in each state have received at least one shot, according to a New York Times vaccine tracker. Still, case counts continue to drop in both states.

Health experts say cases are rising in the Northeast and Upper Midwest for several reasons, including pandemic fatigue, the reopening of schools and the resumption of youth sports.

After difficult starts to the spring, some states, like New Jersey and New York, are showing signs of improvement.

Officials are also concerned about the spread of more contagious virus variants, especially B.1.1.7, first identified in Britain. The variant is now the leading source of new coronavirus infections in the United States, the director of the Centers for Disease Control and Prevention said last week.

Just why those factors might affect some states more than others is hard to pinpoint, experts say.

Dr. David Rubin, the director of PolicyLab at the Children’s Hospital of Philadelphia, said warmer weather in Southern states and California was probably playing a role, because it allows people to gather outdoors, with less risk of transmission.

New case reports have fallen by about 11 percent in Georgia over the past two weeks. And in Alabama, new cases are down roughly 29 percent, with a 17 percent decline in hospitalizations.

Some experts say, though, that reduced testing in some states could be obscuring the true picture. Testing in Alabama, for instance, has started to dip, but the share of tests that come back positive has remained high, at 11.1 percent, compared with a nationwide average of 5.1 percent, according to data compiled by Johns Hopkins University.

“People who are symptomatic and go to their provider are going to get a test,” said Dr. Michael Saag, the associate dean for global health at the University of Alabama at Birmingham, but “the desire for people to go get tested just because they want to know what their status is has dropped off dramatically.”

Still, Dr. Saag said, there is probably not a hidden spike in cases in Alabama right now, since hospitalizations in the state remain low.

People sitting near the Dome of the Rock at the Aqsa Mosque compound, Islam’s third holiest site, in the old city of Jerusalem on Monday.
Ahmad Gharabli/Agence France-Presse — Getty Images

Millions of Muslims on Tuesday began celebrating a second Ramadan in the middle of the pandemic, although in many countries the first day of the holy month offered the promise of a Ramadan with fewer restrictions than last year.

Mosques across the Middle East and other parts of the world were closed for prayer last year, and lockdowns prevented festive gatherings with friends and family. In Jerusalem, for instance, the Old City was largely empty and the Aqsa Mosque compound was closed to the public, as coronavirus cases were surging.

But a large degree of normalcy was back on Tuesday: The Old City’s narrow alleys were crowded, sweet shops were preparing Ramadan desserts, clothing stores were open and the Aqsa compound was welcoming worshipers.

“Last year, I felt depressed and I didn’t know how long the pandemic would last,” said Riyad Deis, a co-owner of a spice and dried fruit shop in the Old City, while selling whole pieces of turmeric and Medjool dates to a customer. “Now, I’m relaxed, I have enough money to provide for my family and people are purchasing goods from my shop — it’s a totally different reality.”

The enthusiasm of some didn’t mean the Ramadan would go as normal. Across several countries in the Middle East, the authorities imposed limitations on customs and festivities, requiring that mosques enforce social distancing and telling worshipers to bring their own prayer rugs and to wear face masks.

In Dubai, Saudi Arabia and Egypt, taraweeh, the optional extra prayers that worshipers can observe at night, were capped at half an hour. No one will also be allowed to spend the night in a mosque, as is common during the last 10 days of Ramadan.

Mosques around the region were also prohibited from serving the fast-breaking meal of iftar or the predawn meal of suhoor. Though Muslims could still gather for those meals with friends and family, the authorities asked them to limit those gatherings this year.

In Jerusalem, Omar Kiswani, the director of Al Aqsa Mosque, said he was overjoyed that the compound was open to worshipers, but still urged caution.

“These are times of great happiness — we hope the blessed Aqsa Mosque will return to its pre-pandemic glory — but these are also times of caution because the virus is still out there,” Mr. Kiswani said.

In Egypt, government officials and prominent television hosts linked to the authorities warned Egyptians of a third wave of infections as Ramadan approached, hinting that another curfew or other lockdown restrictions could be imposed if cases rose.

“If you want the houses of God to remain open,” Nouh Elesawy, an official who oversees mosques at the Egyptian Ministry of Endowments, said earlier this month, “adhere to the precautionary procedures and regulations.”

The Ramadan restrictions may hit the hardest in poor neighborhoods, where residents depend on iftar banquets usually sponsored by wealthy individuals or organizations. For those people, feasting and Ramadan gifts are likely to be rarer, with tourism still at a trickle and many small businesses still suffering from the economic effects of the pandemic.

In Lebanon and Syria, the pandemic has worsened economic crisis that will likely squeeze people’s ability to enjoy the holy month, more than the governments’ limited restrictions aimed at curbing the spread of the coronavirus.

In Syria, where experts say the official infection and death numbers for Covid-19 are far below the reality, the government has few restrictions in place. Worshipers will even be allowed to stand in line inside of mosques to pray together after breaking their fast, the Syrian Ministry of Religious Affairs said.

In Lebanon, which emerged recently from a strict lockdown, shops and restaurants can operate regularly during the day but must offer only delivery service during a nighttime curfew from 9:30 p.m. to 5 a.m.

Kansas City Chiefs head coach Andy Reid during the fourth quarter of the Super Bowl in February. The N.F.L. announced all personnel must be vaccinated or risk losing direct access to players.
Doug Mills/The New York Times

The N.F.L. on Tuesday sent a memo to all 32 teams effectively mandating that support personnel including coaches and trainers be vaccinated against Covid-19, with an exception made for staff who have a “bona fide medical or religious ground” for not doing so.

According to the statement, the unvaccinated will not be allowed to work in proximity to players, who are strongly encouraged, but not yet required, to take the vaccine.

In the most direct address of vaccination protocols so far, the league said it expected employees classified as Tier 1 and Tier 2 — including coaches, trainers, front office personnel, videographers and others — to receive the vaccine. Those tiers were created last summer to stratify and limit access to team facilities as the N.F.L. prepared to open training camps in preparation for the 2020 season, and have been used continually since.

“N.F.L. team facilities proved to be among the safest places in the world in 2020 thanks to N.F.L.-N.F.L.P.A. comprehensive protocols that were developed in conjunction with public health officials,” an N.F.L. spokesman said in a statement emailed to The New York Times. “Having team personnel vaccinated will benefit these individuals and their families, will make the facilities even safer and also provide another step toward returning to normalcy.”

The league will require teams to report how many employees are vaccinated on a weekly basis and, based on those numbers, are expected to relax certain restrictions, such as locker room access, the use of cafeterias and close-contact quarantine, for vaccinated individuals. The memo also encouraged N.F.L. teams to host informational sessions on the vaccine with players, staff members and their families, and to use team stadiums and training facilities as vaccination sites.

The N.F.L.’s mandate follows similar messaging from the N.B.A. and M.L.B., to leagues currently in season, who have incentivized players and personnel with relaxed coronavirus restrictions once they are vaccinated.

Global Roundup

Administering a coronavirus vaccine to a frontline worker in New Delhi, last week.
Rebecca Conway for The New York Times

India said on Tuesday that it would fast-track the approval of vaccines in use in other countries, a move aimed at rapidly increasing the country’s vaccine supply as it battles what is currently the world’s biggest coronavirus outbreak.

The Indian government said that it would grant emergency authorization to any foreign-made vaccine that had been approved for use by regulators in the United States, the European Union, Britain or Japan, or by the World Health Organization. The move had been recommended by a panel of Indian scientists and eliminates a requirement for drug companies to conduct local clinical trials.

“The decision will facilitate quicker access to such foreign vaccines” and encourage imports of materials that would boost India’s vaccine manufacturing capacity, the government said in a statement.

Earlier on Tuesday, India’s top drug regulator granted emergency approval to Sputnik V, the Russian-made vaccine, adding a third vaccine to the country’s arsenal on the same day that health officials recorded 161,736 new coronavirus infections in 24 hours.

It was the seventh straight day that India has added more than 100,000 cases, according to a New York Times database. Only the United States has seen a faster rise in infections during the pandemic.

India has administered about 105 million domestically produced vaccine doses for a population of 1.3 billion, but it is widely believed that the country needs to scale up inoculations rapidly because other measures have failed to control the virus. Many states have reimposed partial lockdowns and weekend curfews. On Tuesday, officials announced that India’s Maharashtra state would have a 15-day shutdown with limits on gatherings, nonessential travel and a ban on public transportation. In Mumbai, within Maharashtra, health officials are racing to erect field hospitals as facilities report shortages of oxygen, ventilators and coronavirus testing kits.

And there is the risk of a superspreading event with the gathering of millions of Hindu pilgrims for the annual Kumbh Mela festival on the banks of the Ganges River, where the authorities say they are powerless to enforce social distancing.

India’s outbreak is reverberating worldwide as its pharmaceutical industry — which was supposed to manufacture and export hundreds of millions of doses of the AstraZeneca vaccine — is keeping most supplies at home. The approval of the Sputnik vaccine, whose first doses are expected to be available for use in weeks, offers hope that India could speed up its inoculation drive.

But it is unclear at this stage whether India will be able to procure significant quantities of other vaccines, including the Pfizer, Moderna and Johnson & Johnson shots in use in the United States. Major Western nations have accumulated much of the global supply of those vaccines and manufacturers are struggling to meet the surging demand.

India will import millions of Sputnik doses from Russia and then begin manufacturing the vaccine domestically, officials said. More than 850 million doses will be made, with some intended for export, Kirill Dmitriev, chief executive of the Russian Direct Investment Fund, a sovereign wealth fund that has financed the vaccine’s development, said in an interview with India’s NDTV channel.

“India is a vaccine-manufacturing hub and our strategic partner for production of Sputnik V,” Mr. Dmitriev said.

India has more than 13.6 million confirmed coronavirus cases, the second most after the United States, and 171,058 deaths, the fourth highest toll.

In other news around the world:

  • Japan has begun vaccinating 36 million people over age 65, the first time shots have been made available to the public during the country’s slow vaccine rollout. Officials said that 1,139 people nationwide had received doses on Monday, and that doses to cover all Japanese above the age threshold would reach municipal health facilities by the end of June. Although Japan has weathered the pandemic better than most countries, the pace of its vaccination effort, which until now had only covered 1.1 million frontline medical workers, has sparked public criticism and raised questions about readiness for the Tokyo Summer Olympics in just over three months.

  • Scotland on Tuesday moved forward plans to loosen its coronavirus lockdown, a day after the British government eased many restrictions in England. New rules beginning Friday will permit Scots to meet outdoors in groups of up to six adults from six households. The current rules restrict travel and set the maximum group size at four, from two households. Restrictions on shops and outdoor service in pubs, now relaxed in England, are scheduled to remain in Scotland until April 26.

  • Austria’s health minister resigned on Tuesday, citing personal health problems that he said have been exacerbated by the grueling job of helping lead the country’s response to the pandemic. “It feels like it has not been 15 months, but 15 years,” the minister, Rudolf Anschober, said in a statement. Mr. Anschober, 60, was appointed in January last year, as a Green party minister in a Conservative-led coalition, and has been one of the main faces of Austria’s coronavirus response. “In the worst health crisis in decades, the republic needs a health minister who is 100 percent fit. That is not currently me,” he said.

  • France will suspend all flights to and from Brazil, because of growing worries about the virus variant spreading there. “We see that the situation is getting worse” in Brazil, Prime Minister Jean Castex told lawmakers. The country previously permitted essential travel from Brazil, subject to testing and isolation requirements.

  • The World Health Organization on Monday evening called on governments to suspend the sale of live wild mammals in food markets to help prevent the emergence of new diseases. “Traditional markets, where live animals are held, slaughtered and dressed, pose a particular risk for pathogen transmission to workers and customers alike,” the agency said in a statement. Animals are the source of more than 70 percent of emerging infectious diseases in humans, it said. Early in the pandemic, Chinese officials suggested that the coronavirus outbreak might have started at a market. But W.H.O. experts said in a report last year that the role of animal markets in the story of the pandemic was still unclear.

Chancellor Angela Merkel, center, at a cabinet meeting in Berlin on Tuesday. Her government’s proposal on coronavirus restrictions would place half the country over the threshold for lockdown.
Pool photo by Andreas Gora

BERLIN — Chancellor Angela Merkel’s government moved a step closer on Tuesday to securing the right to force restrictions on areas where the coronavirus is spreading rapidly, overriding state leaders reluctant to take action.

Ms. Merkel and her ministers approved a legislative proposal that would make it easier for the national government to enforce lockdowns and other limits on movement in regions where infection levels pass a set threshold. At current levels, it could lock down more than half of the country.

Under Germany’s decentralized leadership structures, the 16 state leaders have been meeting regularly with the chancellor to agree on nationwide coronavirus response policies. But with different regions experiencing different rates of infection, some state leaders have been reluctant to enforce the agreed limitations, leading to confusion and frustration among many Germans.

“I believe this amendment is as important as it is an urgent decision about how to proceed in the coronavirus pandemic,” the chancellor told reporters after meeting with her ministers.

Parliament still has to debate and approve the proposal, which would take the form of an amendment to the Protection Against Infection Act, and that process is expected to begin this week.

“We are in a situation where an emergency mechanism is necessary,” Ralph Brinkhaus, the leader of the Christian Democratic Union in Parliament, told reporters, before a meeting of his party lawmakers to discuss the amendment.

Under the proposed amendment, the federal government could force stores and cultural institutions to close and enforce limits on the number of people allowed to meet up in any region where infections surpass 100 new cases per 100,000 residents over a period of seven days.

More controversially, the law would also allow Ms. Merkel’s government to order that schools and day care centers close if the number of new infections reaches more than 200 per 100,000 inhabitants. Schools fall under the jurisdiction of the states, and local leaders are reluctant to relinquish that control.

Germany has registered more than three million infections and more than 78,700 deaths from Covid-19 since the virus began moving through the country last spring. It recorded 10,810 new cases of infection on Tuesday, bringing the national rate of infection to more than 140 per 100,000.

The number of patients in intensive care is expected to hit a record this month, as the country struggles to vaccinate enough people to get ahead of the spread of the highly contagious B.1.1.7 variant.

A woman administrating nasal swabs for the coronavirus test at a mobile testing site in Queens last week.
Shannon Stapleton/Reuters

The number of new coronavirus cases in New York City has remained alarmingly, and stubbornly, high for weeks, even as tens of thousands of people are vaccinated daily.

A likely reason is that more contagious variants have displaced the original forms of the virus, public health officials have said, accounting for more than 75 percent of new cases, according to a recent analysis.

Until this week, the city had not said which variants were more common in which neighborhoods. But newly available ZIP code-level data provides some insight into the mix of variants circulating in the area.

The information serves as a vivid reminder that the dynamics of New York’s epidemic have changed over the past few months, and that the original forms of the virus are increasingly unusual across the city.

A variant first discovered in New York, B.1.526, has spread more widely in the city than all of the others so far. There has also been a significant increase in cases linked to the B.1.1.7 variant, which was first detected in Britain last year and now makes up nearly 30 percent of new cases sequenced in New York City.

This variant is now the main source of new infections across the United States and in Europe.

But not in New York City, where B.1.526 remains the most prevalent variant, making up about 45 percent of cases sequenced from the fourth week of March.

As to which is more contagious — B.1.1.7 or B.1.526 — health officials are not yet sure. “We don’t have enough information to discern this at this moment,” said the city’s health commissioner, Dr. Dave Chokshi.

In a given week, about 1,000 to 2,000 coronavirus cases in New York City are sequenced — that is, the genetic material of the virus is examined for mutations. That represents roughly between 4 and 8 percent of New York City’s new cases. The majority of those cases are sequenced at a laboratory in Long Island City operated by Opentrons, a robotics company.

The city Health Department uses the sequences from this laboratory as the basis for its weekly sample gauging the prevalence of each variant.

But even with thousands of samples sequenced, the data still has significant limitations. Most of its coronavirus samples come from the city’s public hospital system and city sponsored testing sites. It receives lots of samples from some neighborhoods, but few from others.

“The limited number of variants sequenced up till now make it difficult to arrive at conclusions as to whether some neighborhoods are more severely affected than others,” Dr. Wafaa El-Sadr said.

Each dot on the density maps above is placed in the ZIP code of a New Yorker whose coronavirus sample was sequenced at the lab. But neighborhoods with lots of dots do not necessarily correspond with coronavirus hot spots. The density of dots can often be explained by the presence of a city testing center nearby.

On the other hand, neighborhoods with few dots are not necessarily free of variants. It just means few coronavirus samples from there reached the lab.

There are blind spots across the Bronx, Queens and the southern half of Manhattan. In some ZIP codes too few samples have been sequenced to draw any solid conclusions. In Roosevelt Island, for example, only one case has been sequenced.

The city on Monday separately released a report based on ZIP-code level data that also showed the proportion of B.1.1.7 and B.1.526 cases growing rapidly.

The report said that B.1.526 cases have been detected in all five boroughs, but were slightly more common in the Bronx and parts of Queens. B.1.1.7 cases were also found citywide, but were slightly more common in southern Brooklyn, eastern Queens and Staten Island.

City officials said that the maps showed widespread transmission of the variants, and that they were an important reminder for people not to let their guards down in any neighborhood.

“The single best way we can address this threat is by vaccinating everyone as quickly as possible,” said Dr. Jay Varma, a senior adviser on public health in the mayor’s office. “The reality is you are at risk of any of these no matter where you are.”

Lauren Leatherby contributed research.