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In Minnesota, the statewide mask mandate is over. But in Minneapolis, the state’s largest city, face coverings are still required.
On Friday, Rhode Island, North Carolina and Michigan joined the ranks of states, like Kentucky and Oregon, where officials said fully vaccinated people would be able to go out maskless.
But in New York, New Jersey and California, mask mandates remained in force for everyone at least for now.
And in Kansas City, Mo., Mayor Quinton Lucas in a matter of about seven hours said he would not change his mask order, then that he would think about it, then that he was getting rid of it altogether because there was no good way to know who was fully vaccinated and who was not.
“While I understand the C.D.C.’s theory that they could just create a rule that says vaccinated folks go anywhere without a mask, and everybody else who’s unvaccinated will follow it, I don’t know if that’s the type of rule that was written in coordination with anyone who has been a governor or a mayor over the last 14 months,” said Mr. Lucas, a Democrat.
The abrupt decision by the Centers for Disease Control and Prevention to free fully vaccinated people from its mask guidance in most indoor and outdoor settings set off a scramble on Friday across the country to update local rules and redefine social norms.
Major corporations and local shopkeepers weighed whether to take down “masks-required” signs on their doors. People heading to the office or coffee shop or grocery store had to navigate rapidly shifting scientific advice and government restrictions. And surprised state and local officials, including some who withstood months of protests and lawsuits to keep mask orders in place, said they needed time to evaluate the new federal guidance.
In Texas, which lifted mask rules in early March, Chuck Massey, 82, in San Antonio said on Friday that he was comforted by the sight of people wearing masks even after both state and federal officials continue to ease restrictions. Mr. Massey, who suffers from high blood pressure, said he’s taking a “wait and see” approach before he gets the vaccine. But he said he plans to wear a mask no matter what the government says. “The mask is the safest approach, no matter what everyone says,” he said.
In Massachusetts, Joseph Skenderian, one of the owners of Skenderian Apothecary, a pharmacy in Cambridge, smiled on Friday when asked about the agency’s new guidance — visibly, because he was unmasked as he worked with his employees behind a glass partition that separated the group, all fully vaccinated, from any customers. He said he and the workers would continue wearing masks with customers until officials said that people no longer needed to be masked in medical facilities.
He said he trusted that the C.D.C. was being guided by science and data, and so he took the new policy as a sign of how far things have come. “I am personally ecstatic about it because I didn’t think this would happen for another year,” he said, “so I think we’ve had tremendous success with the vaccine and everything we’ve done.”
For more than a year, masking had been urged by public health experts, a key to stopping the airborne spread of the coronavirus. Some places allowed their mask requirements to expire months ago, but face coverings remained mandatory in some form in more than 20 states, as well as many cities and counties. Just a few weeks ago, the C.D.C. said fully vaccinated Americans could usually forego masks outdoors, but should continue wearing them in public spaces indoors.
The agency changed course on Thursday, saying people who were at least two weeks past their final dose of a vaccine could safely go most places, both indoors and outdoors, without a mask. The C.D.C. said everyone should still wear a mask in certain settings, including health care facilities, on public transportation and on flights.
The reversal left officials at all levels of government scrambling, with a fast-moving series of announcements and news conferences that continued through midday Friday. Many public health experts and local officials said they were puzzled about how to implement the new advice since there was no national system for differentiating the people who are fully vaccinated — now 36 percent of Americans — from the 64 percent who are not.
In Congress, the Capitol’s attending physician said fully vaccinated members could “resume activities that you did prior to the pandemic,” but that a mask mandate on the House floor would remain in place. And in Nevada, the state’s Gaming Control Board said it would leave mask rules up to individual businesses, and that it was “not practical for the Board to attempt to enforce a mask mandate tethered to an individual’s vaccination status.”
Edgar Sandoval and Kate Taylor contributed reporting.
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U.S. vaccinations ›
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LONDON — Prime Minister Boris Johnson of Britain said on Friday that vaccination protocols would be changed to swiftly deliver second doses to people over 50-years-old to combat the spread of a coronavirus variant first detected in India, a warning sign for countries that are easing restrictions even though their own vaccination campaigns are incomplete.
“We believe this variant is more transmissible than the previous ones,” Mr. Johnson said. What remained unclear, he said, was by how much. The infectiousness of the variant first detected in India remains the subject of intense study and some leading experts have said it is too early to assess its transmissibility.
If it proves significantly more transmissible, he said, “we face some hard choices.” He added that there was no evidence that the variant was more likely to cause serious illness and death, and there was no evidence to suggest vaccines were less effective against the variant in preventing serious illness and death.
While he said the country would not delay plans to ease restrictions on Monday, he warned that the spread of the variant could force the government to change course.
“This new variant could pose a serious disruption to our progress,” he said at a news conference on Friday.
The numbers of cases involving the variant, known as B.1.617, rose from 520 last week to 1,313 cases this week in Britain, according to official statistics.
The extent to which the variant has spread globally is unclear, because most countries lack the genomic surveillance capabilities employed in England.
That surveillance capability has allowed health officials in Britain to spot the rise of concerning variants more quickly than other nations, offering an early warning system of sorts as a variant seen in one nation almost invariably pops up in others.
Most cases detected in Britain are in northwestern England. The focus has been on Bolton, a town of nearly 200,000 that has one of the country’s highest rates of infection and where health officials have warned of widespread community transmission of the variant. Some cases have also been reported in London. The rapid spread of the variant has led officials to debate speeding up dosing schedules and opening up access to shots in hot spots to younger age groups.
National restrictions in England are scheduled to be eased on Monday, with indoor dining and entertainment returning, before a full reopening in June. But officials have cautioned that those plans might be in danger.
In Scotland, First Minister Nicola Sturgeon said on Friday that plans to ease restrictions in Glasgow would be delayed at least a week out of concern about an uptick in cases that officials said may be being driven by the variant.
Much is unknown about the new variant, but scientists fear it may have driven the rise of cases in India and could fuel outbreaks in neighboring countries.
Dr. Maria Van Kerkhove, the technical lead of the World Health Organization’s coronavirus response, said a study of a limited number of patients, which had not yet been peer-reviewed, suggested that antibodies from vaccines or infections with other variants might not be quite as effective against B.1.617. The agency said, however, that vaccines were likely to remain potent enough to provide protection from serious illness and death.
British officials have said the variant appears to be more contagious than the B.1.1.7 variant, which was detected last year in Kent, southeast of London and swept across Britain in the winter, forcing the country into one of the world’s longest national lockdowns. The B.1.1.7 variant has now been found in countries around the world.
The B.1.617 variant has been found in virus samples from 44 countries and was designated a variant of concern by the W.H.O. this week, which means there is some evidence that it could have an impact on diagnostics, treatments or vaccines and needs to be closely monitored.
Christina Pagel, a member of a group of scientists advising the government, known as SAGE, said postponing next week’s reopening would avoid “risking more uncertainty, more damaging closures and longer recovery from a worse situation.”
“We need to learn from previous experience,” Dr. Pagel, the director of the Clinical Operational Research Unit at University College London, said on Twitter.
Britain briefly reopened its economy at the end of last year, only to abruptly impose new restrictions that remained in place for months as it fought a deadly wave of infections.
In an attempt to offer at least partial protection to as many people as quickly as possible, Britain spaced injections between doses for two-stage coronavirus vaccines up to 12 weeks after the first vaccines were approved in December. That was far longer than the three- or four-week interval employed by most other countries.
Mr. Johnson said that those older than 50 will now be able to get second doses after eight weeks.
“It is more important than ever that people get the additional protection of a second dose,” he said.
The speedy rollout saved at least 11,700 lives and prevented 33,000 people from becoming seriously ill in England, according to research released by Public Health England on Friday.
Infections, serious illness and deaths have plummeted across Britain. Only 17 deaths were reported on Friday.
But the vaccination campaign has slowed down since last month because of supply shortages and the need to start distributing second doses. The number of daily first doses on average last month was 113,000, far below the average of 350,000 daily doses administered in March.
Only those over 38-years-old are currently eligible for vaccination.
It remains unclear whether the country has the vaccine supplies on hand to move rapidly to surge more into communities around the country to speed up vaccinating younger age groups.
Correction: May 14, 2021
An earlier version of this item misstated the affiliation of Christina Pagel, a science adviser. Ms. Pagel is a member of Independent SAGE, a group of expert advisers unaffiliated with the government. She is not a member of SAGE, a panel of government advisers.
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BUENOS AIRES — For most of the past year, Uruguay was held up as an example for keeping the coronavirus from spreading widely as neighboring countries grappled with soaring death tolls.
Uruguay’s good fortune has run out. In the last week, the small South American nation’s Covid-19 death rate per capita was the highest in the world, according to data compiled by The New York Times.
As of Wednesday, at least 3,252 people had died from Covid-19, according to the Uruguayan Health Ministry, and the daily death toll has been about 50 during the past week.
Six out of the 11 countries with the highest death rates per capita are in South America, a region where the pandemic is leaving a brutal toll of growing joblessness, poverty and hunger. For the most part, countries in the region have failed to acquire sufficient vaccines to inoculate their populations quickly.
Contagion rates in Uruguay began inching up in November and soared in recent months, apparently fueled by a highly contagious variant first identified in Brazil last year.
“In Uruguay, it’s as if we had two pandemics, one until November 2020, when things were largely under control, and the other starting in November, with the arrival of the first wave to the country,” said José Luis Satdjian, the deputy secretary of the Health Ministry.
The country with the second-highest death rate per capita is nearby Paraguay, which also had relative success in containing the virus for much of last year but now finds itself in a worsening crisis.
Experts link the sharp rise in cases in Uruguay to the P.1 virus variant detected in Brazil.
“We have a new player in the system and it’s the Brazilian variant, which has penetrated our country so aggressively,” Mr. Satdjian said.
Uruguay closed its borders tightly at the beginning of the pandemic, but towns along the border with Brazil are effectively binational and have remained porous.
The outbreak has strained hospitals in Uruguay, which has a population of 3.5 million.
On March 1, Uruguay had 76 Covid-19 patients in intensive care units. This week, medical professionals were caring for more than 530, according to Dr. Julio Pontet, president of the Uruguayan Society of Intensive Care Medicine who heads the intensive care department at the Pasteur Hospital in Montevideo, the capital.
That number is slightly lower than the peak in early May, but experts have yet to see a steady decline that could indicate a trend.
“It is still too early to reach the conclusion that we’ve already started to improve, we’re in a high plateau of cases,” Dr. Pontet said.
Despite the continuing high number of cases, there is optimism that the country will be able to get the situation under control soon because it is one of the few in the region that has been able to make quick progress on its vaccination campaign. About a quarter of the population has been fully immunized.
“We expect the number of serious cases to begin decreasing at the end of May,” Dr. Pontet said.
Credit…Jim Wilson/The New York Times
Once Americans return to crowded offices, schools, buses and trains, so too will their sneezes and sniffles.
Having been introduced to the idea of wearing masks to protect themselves and others, some Americans are now considering a behavior scarcely seen in the United States but long a fixture in other cultures: routinely wearing a mask when displaying symptoms of a common cold or the flu, even in a future in which Covid-19 isn’t a primary concern.
Such routine use of masks has been common for decades in other countries, primarily in East Asia, as protection against allergies or pollution, or as a common courtesy to protect nearby people.
Leading American health officials have been divided over the benefits, partly because there is no tidy scientific consensus on the effect of masks on influenza virus transmission, according to experts who have studied it.
Nancy Leung, an epidemiologist at the University of Hong Kong, said that the science exploring possible links between masking and the emission or transmission of influenza viruses was nuanced — and that the nuances were often lost on the general public.
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SINGAPORE — Singapore said on Friday that it would ban dining in restaurants and gatherings of more than two people to try to stem a rise in coronavirus cases, becoming the latest Asian nation to reintroduce restrictions after keeping the illness mostly in check for months.
The new measures came after the city-state recorded 34 new cases on Thursday, a small number by global standards, but part of a rise in infections traced to vaccinated workers at Singapore Changi Airport.
The airport outbreak began with an 88-year-old member of the airport cleaning crew who was fully vaccinated but who tested positive for the virus on May 5. Co-workers who then became infected later visited an airport food court, where they transmitted the virus to other customers, officials said.
None of the cases linked to the airport outbreak are believed to have resulted in critical illness or death, according to officials.
In all, 46 cases have been traced to the airport, the largest of about 10 clusters of new infections in the country.
“Because we do not know how far the transmission has occurred into the community, we do have to take further, more stringent restrictions,” said Lawrence Wong, co-chair of Singapore’s coronavirus task force. The measures will be in effect for about one month beginning on Sunday.
According to preliminary testing, many of those infected were working in a zone of the airport that received flights from high-risk countries, including from South Asia. Several have tested positive for the B.1.617 variant first detected in India, which the World Health Organization has said might be more contagious than most versions of the coronavirus.
Singapore health officials said that of 28 airport workers who became infected, 19 were fully vaccinated with either the Pfizer or Moderna vaccines, the only two approved for use in Singapore.
“Unfortunately, this mutant virus, very virulent, broke through the layers of defense,” Transport Minister Ong Ye Kung told a virtual news conference on Friday.
Mr. Ong also said that the rise in cases “very likely” means that a long-delayed air travel bubble with Hong Kong would not begin as scheduled on May 26.
Singapore, a prosperous island hub of 5.7 million people, saw an explosion of infections among migrant workers living in dormitories, but a two-month lockdown and extensive testing and contact tracing contained the outbreak. Although Singapore has kept much of its economy open, its vaccination effort has not moved as quickly as many expected: less than one-quarter of the population has been fully inoculated.
Changi Airport, which served more than 68 million passengers in 2019, is operating at 3 percent of capacity as Singapore has paused nearly all incoming commercial traffic. Employees there work under strict controls, wearing protective gear and submitting to regular coronavirus tests.
Singapore joins Japan, Thailand and other Asian countries that have struggled to contain new outbreaks fueled in part by variants. But Paul Ananth Tambyah, president of the Asia Pacific Society of Clinical Microbiology and Infection, said that the rise in cases was not overly worrying.
“The reason for my optimism is that we now have effective vaccines, better diagnostics, proven treatments and even potential prophylactic agents,” he said. “If these are employed in a targeted approach, it is unlikely that we will end up with the same problems we had last year.”
Credit…Atul Loke for The New York Times
After shortages in oxygen in New Delhi led to scores of people dying in hospitals, officials said there was now enough supply in the Indian capital to start sharing a surplus of the lifesaving gas to needier parts of the country.
For weeks, the New Delhi government appealed to Prime Minister Narendra Modi for a larger share of India’s oxygen reserves, with the battle for air ending up in the nation’s highest court.
On Thursday, just days after receiving the amount it had requested, New Delhi’s second-highest official, Manish Sisodia, said the city’s demand had fallen and its excess supply should be reallocated.
“The number of cases is coming down, hospital bed occupancy is coming down, and demand for oxygen, too, is down,” Mr. Sisodia told The New York Times.
It was an indication that the crisis in the capital might be reaching a peak.
The oxygen shortage in New Delhi began in April and has been linked to dozens of deaths, in and out of hospitals.
Health care facilities and crematories were overwhelmed, and medical professionals and residents were left scrambling for scarce resources.
Thousands of people in the city of 20 million stood in line at oxygen refilling stations, bringing cylinders into hospitals for friends and family or hoarding them at home in case the need arose.
The rise of new coronavirus infections in India has slowed. But, in pattern seen in nation after nation battered by the virus, death rates often plateau a few weeks later. And with the virus spreading in low-income rural areas, the overall crisis shows no sign of abating.
As of Wednesday, the official death toll surpassed 258,000, although experts suspect the true number to be much higher.
As the smoke from New Delhi crematories starts to clear, dozens of bodies have surfaced along the holy Ganges River in the states of Uttar Pradesh and Bihar.
Krishna Dutt Mishra, an ambulance driver in the Bihari village of Chausa, said that poor people were disposing of bodies in the river because the cost of cremations had become prohibitively expensive.
On Friday, the Indian news media showed bodies wrapped in cloth of the saffron color, considered auspicious in Hinduism, buried in shallow graves on the sandy banks of the Ganges River in the Unnao district of Uttar Pradesh.
Priyanka Gandhi, a leader of the opposition Indian National Congress party, called for a High Court investigation, saying that what was happening in Uttar Pradesh was “inhuman and criminal.”
Credit…Saul Martinez for The New York Times
Latino adults in the United States have the lowest rates of Covid-19 vaccination, but among the unvaccinated they are the demographic group most willing to receive the Covid shots as soon as possible, a new survey shows.
The findings suggest that their depressed vaccination rate reflects in large measure misinformation about cost and access, as well as concerns about employment and immigration issues, according to the latest edition of the Kaiser Family Foundation Covid-19 Vaccine Monitor.
Earlier polls had suggested that skepticism about the vaccine was widespread among Latinos, but the latest survey showed that hesitation is declining.
Nearly 40 percent of all the unvaccinated Latinos responding to the survey said they feared they would need to produce government-issued identification to qualify. And about a third said they were afraid that getting the shot would jeopardize either their immigration status or that of a family member.
Their responses also pointed to the importance of community-based access. Nearly half said they would be more likely to be vaccinated if the shots were available at sites where they normally go for health care.
Credit…Rick Bowmer/Associated Press
Throughout the pandemic, few topics have touched so raw a nerve in the United States as mask wearing. Confrontations have erupted from state capitols to supermarket checkout aisles, and debates raged over whether mask mandates violate First Amendment rights.
The Centers for Disease Control and Prevention provoked a flood of reaction with its announcement on Thursday that Americans who are fully vaccinated may stop wearing masks or maintaining social distance in most indoor and outdoor settings. Here’s a sampling, edited for length and clarity, of how Times readers reacted to the news on Facebook and on our website:
“I think this is a good incentive for the hesitators. Hopefully they’ll want to participate in activities (the ones that require proof of vaccination) maskless, so perhaps this will be an incentive, as they see others in the community enjoying life more.” writes Jerry B., on Facebook.
“Very, very few people have been wearing masks for the past 6 months. Covid is a real risk — I certainly don’t want it — but our cases have dropped precipitously, even with minimal masking. This announcement is welcome — the world will not end if people stop masking,” writes Stephen from Oklahoma City.
“I see the need for this policy change, but I fear that the cheaters — those who are not vaccinated but pretend to be — will be the ruin of us all,” writes Cary in Oregon.
“I have my doubts about the incentivization bit,” writes Andrew from Colorado Springs, Colo. “I figure it will simply mean that suddenly everyone’s been fully vaccinated, true or not. That said, as a double-shotted person, I figure my chances of being taken out by an anti-vaxxer are now less than my chances of being taken out by a texting driver. I’m down with that.”
“What’s to stop anti-masker/anti-vaxxer contrarians from mingling unmasked with the vaccinated population? I have little trust in this,” writes Mary Beth in Santa Fe, N.M.
“I am fully vaccinated and caught Covid anyway. I do think it made my symptoms more mild, but you can bet your bippy I’m going to be wearing my mask when I am out of quarantine.” — writes Jaime P., on Facebook.
What do you think about the guidance? Join the conversation.
Kevin Hayes contributed research.
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Gleyber Torres, the Yankees’ two-time All-Star shortstop, became the eighth person involved with the Yankees organization to test positive for the coronavirus this week, the team announced on Thursday. But what has caught the attention of many outside of the baseball world is that Torres, three coaches and four support staff members had all been fully vaccinated.
The Yankees have called all eight instances “breakthrough positives.” According to the Centers for Disease Control and Prevention, a breakthrough case occurs when a fully vaccinated person contracts the virus. It said a small number of such cases would be expected despite the effectiveness of vaccines, because none of the vaccines are capable of preventing illness in 100 percent of cases.
It’s not immediately clear how this happened.
The Yankees had been enjoying relaxed health and safety protocols under rules negotiated by M.L.B. and the players’ union for reaching a threshold at which 85 percent of the team’s players and key personnel were fully vaccinated.
When asked about a possible common thread among the positive cases, Cashman pointed to a long rain delay before a game at Yankee Stadium on Saturday and said that players had a much larger clubhouse space indoors to spread out in compared to what the coaches and the support staff had. A day later, the team flew to Tampa.
Dr. Rochelle P. Walensky, the C.D.C.’s director, said on Thursday that the agency wanted to learn more about the Yankees’ outbreak. She pointed to the fact that six of the Yankees’ seven cases as of Wednesday were asymptomatic, suggesting that proved that the vaccine was indeed effective.
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Gov. Ron DeSantis of Florida said on Wednesday that he would pardon “any Floridian” who violated mask or social distancing mandates.
Mr. DeSantis, a Republican, made the announcement during an appearance on the Fox News program “Ingraham Angle,” just a day before the Centers for Disease Control and Prevention shifted its guidelines to allow vaccinated people to skip wearing masks in most places.
The show’s host, Laura Ingraham, first interviewed Mike and Jillian Carnevale, the owners of a Broward County gym, who said they had been arrested for violating a county mask mandate. Mr. DeSantis then said their case was “a total overreach.”
Widely seen as positioning himself as a 2024 Republican presidential nominee, Mr. DeSantis throughout the pandemic has criticized coronavirus restrictions and mandates.
Mr. Carnevale said he and Ms. Carnevale were arrested three times after violating Broward County’s mask mandate. Mr. Carnevale was charged with two second-degree misdemeanors and if convicted would face a 120-day jail sentence, and Ms. Carnevale was charged with one second-degree misdemeanor, facing 60 days in jail, said Cory Strolla, a lawyer representing the couple.
Last month, Mr. DeSantis issued an executive order prohibiting businesses from requiring patrons or customers to show vaccination documentation, or risk losing grants or contracts funded by the state. Norwegian Cruise Line, which is requiring all guests and crew members to be vaccinated, said it was considering skipping Florida ports over the order.
Credit…Max Whittaker for The New York Times
The Biden administration on Thursday outlined how it will spend $7 billion to expand the nation’s public health workforce, adding tens of thousands of jobs to respond to the Covid-19 pandemic and future outbreaks, including disease investigators, contact tracers and epidemiologists.
Over $4 billion will go to state and local health departments to help with their Covid-19 response, the White House said in a news release, allowing them to “quickly add staff.” Hiring would include vaccine and test administrators, data scientists, epidemiologists and school nurses who can work to vaccinate teens and children in the coming months. Some of the hiring will boost the ranks at the Epidemic Intelligence Service, the vaunted arm of the Centers for Disease Control and Prevention that investigates disease outbreaks.
“Though many threats have increased in complexity and scale in recent years, our nation’s public health workforce has gotten smaller,” Dr. Rochelle Walensky, the C.D.C. director, said at a White House news conference Thursday. “This support will immediately add more staff in health departments across the country.”
C.D.C. leaders have long complained of neglect and underfunding, saying that lawmakers typically only send more resources to the agency when there is a dire public health emergency. Other federal health agencies, particularly the National Institutes of Health, are significantly better funded. Many local health departments have also been short on funding for years.
State and local governments would be able to decide how they use the money, which was allocated through the American Rescue Plan, said Carole Johnson, the Biden administration’s testing coordinator.
The funding underscored a sharp contrast with the Trump administration, which routinely sought to cut off congressional funding for the C.D.C. and stifle its independence within the Department of Health and Human Services.
And it offered relief for local health departments that have been sapped by low morale, firings and harassment. One challenge, though, might be finding enough qualified people to fill new job openings.
Ms. Johnson said money could also go to increasing the number of “disease intervention specialists,” or health workers who would conduct contact tracing, work on case management and help with outbreak investigations. And $400 million would go to a new partnership between the C.D.C. and AmeriCorps, a sprawling national service organization. Called Public Health AmeriCorps, the program would form a “pipeline” for public health workers.
The administration was providing another $3 billion to a new C.D.C. grant program to help smaller local health departments keep staff. The grants would allow those hired to help with the coronavirus pandemic to “continue their careers beyond the pandemic as public health professionals,” the White House said.
“We really are asking grantees to prioritize recruiting from communities they serve and backgrounds that are underrepresented,” Ms. Johnson said.
Credit…Allison Zaucha for The New York Times
The Pfizer-BioNTech and Moderna coronavirus vaccines are 94 percent effective at preventing symptomatic Covid-19 illness, according to a new study of more than 1,800 health care workers in the United States.
The research, which the Centers for Disease Control and Prevention released on Friday, provides yet more evidence that the vaccines are working well even outside controlled clinical trials.
“This report provided the most compelling information to date that Covid-19 vaccines were performing as expected in the real world,” Dr. Rochelle Walensky, the C.D.C. director, said in a statement on Friday.
“This study, added to the many studies that preceded it, was pivotal to C.D.C. changing its recommendations for those who are fully vaccinated against Covid-19.”
The findings are based on an ongoing study of health care workers in 25 states. This interim analysis included data on 1,843 health care workers who were routinely tested for infection with the coronavirus. More than 80 percent of participants were female.
Some 623 workers tested positive between January and mid-March. Those who were fully vaccinated were 94 percent less likely to develop symptomatic coronavirus infections than their unvaccinated peers, the researchers found. The figures are consistent with the efficacy estimates from the clinical trials.
The scientists also found that a single dose of the two-shot regimen was 82 percent effective at preventing symptomatic infection. That figure is higher than has been reported in other studies and may be a result of the relative youth of the study participants, who had a median age of 37 to 38. Fewer than 2 percent were 65 or older.
C.D.C. scientists had previously found that fully vaccinated health care, frontline and essential workers were 90 percent less likely to contract the coronavirus. Those findings helped allay fears that vaccinated people might still be likely to carry the virus, even asymptomatically, and spread it to others.
The concern was one of the main rationales for asking vaccinated Americans to continue to wear masks, a recommendation that the C.D.C. lifted on Thursday.