The suspension of the use of the AstraZeneca Covid-19 vaccine by most governments across Europe has further set back an already fraught inoculation campaign on the continent even as the bloc’s main drug regulator said there was no indication that vaccination has caused side effects such as blood clots.
No country in the European Union is on pace to reach its goal of vaccinating 70 percent of its population by September. Hundreds of millions of people across the continent are still constrained by some of the most severe coronavirus restrictions in the world, and millions more are facing the prospect of rules being tightened further to tackle a third wave of the coronavirus.
The head of the European Medicines Agency said on Tuesday that regulators were still studying concerns about the possibility of rare side effects with the AstraZeneca vaccine, including blood clots and abnormal bleeding. But there was “no indication that vaccination has caused these conditions,” Emer Cooke, the agency’s executive director, told a news conference.
“While the investigation is ongoing, we are currently still firmly convinced that the benefits of the AstraZeneca vaccine in preventing Covid-19, with its associated risk of hospitalization, outweigh the risk of the side effects,” she added.
The reassurance, a day after several major European countries suspended AstraZeneca vaccinations, added to the confusion and mixed messages surrounding the continent’s vaccine rollout. The stakes could scarcely be higher — delaying shots to tens of millions of people in the midst of a third wave of the virus and possibly undermining public confidence in the vaccine, which could have implications far beyond Europe.
The European Union’s vaccine efforts have been marked by political infighting, mixed messaging to the public, a shortage of supply and a lack of solidarity. And with many member states’ vaccination strategies heavily reliant on the vaccine made by AstraZeneca, the decision to suspend its use while the bloc’s regulatory body looks into concerns about its safety will slow things down even more.
Spain, France, Italy, Germany and others have halted the use of AstraZeneca’s vaccine. All of the governments in Europe that suspended it said they were acting out of an abundance of caution while the bloc’s regulatory body reviewed the data.
The World Health Organization was quick to react to moves by European governments, hoping to prevent a broader panic. It said on Monday that there was no evidence to suggest that the AstraZeneca vaccine was unsafe.
Millions of people in dozens of countries have received AstraZeneca’s Covid vaccine with few reports of ill effects, and its prior testing in tens of thousands of people found it to be safe.
The AstraZeneca vaccine, developed in partnership with Oxford University, was designed to be the workhorse of the global vaccination effort — with some two billion doses ordered for use in more than 70 countries this year.
It is being sold using a nonprofit model and is far cheaper than other vaccines. It can be stored more easily and has already started to be shipped to low- and middle-income countries that signed onto the global vaccine sharing program Covax.
As of Sunday, the European Union had nearly eight million doses of AstraZeneca vaccine sitting unused, according to the European Centre for Disease Prevention and Control. The 27 nations in the bloc, and three close neighbors, have between them vaccinated roughly 42 million people.
In contrast, the United States is now vaccinating more than 2.4 million people every day, with more than 100 million doses administered already.
While the AstraZeneca vaccine is already authorized in dozens of countries, it has not yet been approved by American regulators. The results from its clinical trial in the United States have not yet been reported, and the company has not sought emergency use authorization from the Food and Drug Administration.
While some countries have suspended the use of AstraZeneca’s coronavirus vaccine over safety concerns, Thailand on Tuesday kicked off a program for its distribution nationwide, with Prime Minister Prayuth Chan-ocha receiving the first shot.
Thailand is one of several countries, including Australia and India, that are continuing to use the AstraZeneca vaccine as experts investigate reports of fatal brain hemorrhages and blood clots among a handful of people who received it. Millions of people around the world have been inoculated with the AstraZeneca vaccine, and scientists say there is no evidence that it causes blood clots, which can occur for any number of reasons.
More than a dozen countries, mostly in Europe, have paused AstraZeneca vaccinations in the last few days, raising fears that vaccinations will be disrupted at a critical time. In Asia, Indonesia also said on Monday that it would not start distributing the AstraZeneca vaccine until it could determine that it was safe.
The AstraZeneca vaccine, which has been authorized in more than 70 countries, is seen as key to fighting the virus in the developing world because it is cheaper and easier to store than other vaccines.
Thailand on Friday became the first country outside Europe to delay use of the AstraZeneca vaccine, which Mr. Prayuth had been scheduled to receive that day. By Monday, however, officials said they had received information from the World Health Organization and the European Medicines Agency confirming that the vaccine was not connected to the occurrence of blood clots and was safe to use.
In an event on Tuesday that was broadcast online, Mr. Prayuth, 66, selected a vial from a box of AstraZeneca vaccines, inspected the label and received his shot as officials around him applauded.
“I feel good,” he said moments later. “This will build confidence for the general public in the government vaccination program.”
AstraZeneca is one of two vaccines authorized for use in Thailand, with the Thai company Siam Bioscience expected to produce 61 million doses by the end of the year.
Other countries agree that there is insufficient evidence to justify suspension. In a statement on Tuesday, the Australian medicines regulator said it had not received any reports of blood clots among people who had received the AstraZeneca vaccine. Greg Hunt, the health minister, also said the government supported continued use of the shot.
“There have been views expressed — we disagree with them clearly, absolutely, unequivocally,” he said in Parliament.
AstraZeneca is central to Australia’s vaccination drive, with most of the 53.8 million doses the government has secured being manufactured domestically.
Officials in India, where the AstraZeneca vaccine is manufactured locally and known as Covishield, have said there is no immediate concern. They are reviewing data on adverse effects for the AstraZeneca vaccine and for the other shot being used, a domestic vaccine called Covaxin.
Ohio and Indiana are the latest states to announce significant expansions in Covid-19 vaccine eligibility for their residents. In Ohio, eligibility will be extended to anyone 40 years and older as of Friday, as well as for residents with certain medical conditions, including cancer, chronic kidney disease and heart disease. Indiana extended its group of eligible residents to people 45 and older, effective immediately. And Wisconsin on Tuesday said residents 16 years and older with certain medical conditions will be eligible for vaccinations a week earlier than initially planned.
President Biden has called on states to offer vaccines to all adults by May 1 and has said that the United States will have secured enough doses by the end of May for shots to be made available to them. And several states across the country have already begun expanding the criteria for vaccinations.
In Indiana, where new coronavirus cases, hospitalizations and deaths have decreased, 20 percent of the population has had at least one dose, and 11 percent is fully vaccinated, according to a New York Times analysis of data from the Centers for Disease Control and Prevention.
The pace of vaccinations in both Indiana and Ohio is comparable to the national pace of vaccinations, according to a Times database.
In Ohio, as of Monday, about 21 percent of adults in the state had received at least one shot and 12 percent were totally vaccinated, according to a Times database.
Gov. Mike DeWine of Ohio, a Republican, announced the expanded eligibility on Tuesday, as well as a goal of working up to administering 6,000 shots a day across the state in the coming days, an increase over the 1,500 shots a day he said the state is currently administering.
With the expanded criteria, Mr. DeWine said another 1.5 million Ohio residents will be eligible for the vaccine on Friday. He also said a new Federal Emergency Management Agency mass vaccination site, the Cleveland State University’s Wolstein Center, would handle shots for more than 200,000 people over the next eight weeks.
“I want to thank the president, President Biden, for making this site available to us,” Mr. DeWine said during a news conference on Tuesday.
New virus cases, hospitalizations and deaths in the state have been on the decline, according to Times data. Over the past 7 days, Cuyahoga County, which includes Cleveland and is Ohio’s second-largest county, has had the most new cases, and public health experts gauge the risk of getting Covid-19 there as very high, based on a Times analysis. Putting a mass vaccination site in the county and on Cleveland State’s campus, he said, was a deliberate move, given its proximity to some underserved neighborhoods. Mr. DeWine said free transportation to and from the Wolstein Center would be provided.
Ohio will make vaccines eligible to all Ohio residents 16 years and older on March 29.
The drug company Moderna has begun a study that will test its Covid vaccine in children under 12, including babies as young as six months old, the company said on Tuesday.
The study is expected to enroll 6,750 healthy children in the United States and Canada. Moderna declined to say how many had already signed up or received the first shots, according to a spokeswoman, Colleen Hussey.
“There’s a huge demand to find out about vaccinating kids and what it does,” said Dr. David Wohl, the medical director of the vaccine clinic at the University of North Carolina, who is not involved the study.
In a separate study, Moderna is testing its vaccine in 3,000 children ages 12 to 17 years, and may have results for that age group by summer. The vaccine would then have to be authorized for use in children, so it would not be immediately available.
Many parents want protection for their children, and vaccinating children should help to produce the herd immunity considered crucial to stopping the pandemic. The American Academy of Pediatrics has called for expansion of vaccine trials to include children.
Vaccine side effects like fever, sore arms, fatigue and achy joints and muscles can be more intense in children than in adults, and doctors say it is important for parents to know what to expect after their children are inoculated.
Each child in Moderna’s study will receive two shots, 28 days apart. The study will have two parts. In the first, children ages 2 years to less than 12 may receive two doses of 50 or 100 micrograms each. Those under 2 years may receive two shots of 25, 50 or 100 micrograms. (One adult dose is 100 micrograms.)
In each group, the first children inoculated will receive the lowest doses and will be monitored for reactions before later participants are given higher doses.
Then, researchers will perform an interim analysis to determine which dose is safest and most likely to be protective for each age group.
Children in part two of the study will receive the doses selected by the analysis — or placebo shots consisting of salt water.
Moderna developed its vaccine in collaboration with the National Institute of Allergy and Infectious Diseases. The company and the institute are also working together on the study, along with the federal Biomedical Advanced Research and Development Authority.
The children will be followed for a year, to look for side effects and measure antibody levels that will help researchers determine whether the vaccine appears to provide protection. The antibody levels will be the main indicator, but the researchers will also look for coronavirus infections, with or without symptoms.
Dr. Wohl said the study appeared well designed and likely to be efficient, but he questioned why the children were to be followed for only one year, when adults in Moderna’s study are followed for two years. He also said he was somewhat surprised to see the vaccine being tested in children so young this soon.
“Should we learn first what happens in the older kids before we go to the really young kids?” Dr. Wohl asked. Most young children do not become very ill from Covid, he said, though some develop a severe inflammatory syndrome that can be life threatening.
Johnson & Johnson has also said it would test its coronavirus vaccine in babies and young children after testing it first in older children.
Pfizer and BioNTech are testing their vaccine in children ages 12 to 15, and have said the plan is to move to younger groups; the product is already authorized for use in those 16 and up in the United States.
Last month, AstraZeneca began testing its vaccine in Britain in children 6 years and older.
In a city scrambling to vaccinate people against Covid-19, Ambar Keluskar faced a problem that seemed to defy logic: The pharmacist, based in Brooklyn, struggled to find people to take the 200 doses he had on hand this month.
State rules restricted who could get shots at independent pharmacies like his to certain older residents, and fewer and fewer people seemed to be scheduling appointments. The problem was even more vexing because his pharmacy, Rossi Pharmacy, draws many customers from East New York — a community that has been hit hard by the pandemic, and whose vaccination rate lags behind other parts of New York City.
Mr. Keluskar’s pharmacy spent hundreds of dollars on Facebook advertisements to let people know that he had available doses. He asked community leaders to spread the word. Then he decided to try a different approach: Instead of waiting for people to come to the pharmacy, he would take his doses to them.
Vaccine providers and would-be recipients alike have been confronted by bureaucratic eligibility rules, a shifting understanding of the virus and a sign-up system that can be prohibitively complex. Vaccinations have been slower to reach many communities where the virus has inflicted the highest toll, and where people may not have the time or resources to easily sign up for appointments.
In response to these problems, volunteers and community groups have built appointment websites, hosted pop-up clinics at churches and helped eligible neighbors navigate the process.
Among those seeking to fill that void was Mr. Keluskar, who this month vaccinated almost 50 people at a senior affordable housing complex near downtown Brooklyn who were homebound or struggling to find appointments.
“The patients loved it,” he said. “They got to get vaccinated somewhere local.”
Papua New Guinea, which had largely avoided the coronavirus, is now sounding the alarm over an outbreak that its prime minister said could infect up to a third of the country’s population.
The small island nation has recorded 2,269 coronavirus cases and 26 deaths since the beginning of the pandemic, according to the country’s health department. Nearly half of the infections were recorded in the last two weeks, and 97 cases were reported on Sunday.
On Monday, Prime Minister James Marape called the situation “critical” and said that restrictions on movement would be brought in. The nation’s businesses will be allowed to remain open, but residents will not be allowed to leave their provinces or villages.
Only about 55,000 of the nation’s nine million people have been tested for the coronavirus, a low rate that signals the actual number of infections may be much higher than reported.
There are also concerns that the country’s fragile health system will buckle under the strain, and that recently held gatherings to commemorate former Prime Minister Michael Somare, who died last month, would become super-spreader events.
The spike in cases has prompted concerns in neighboring Australia that the outbreak could spread to its shores. The Torres Strait Islands, an autonomously administered group of islands, are just two and a half miles from Papua New Guinea at the nearest point.
Aid groups and Australia’s opposition party have urged the government to provide emergency vaccine doses to Papua New Guinea. The smaller nation has sourced 200,000 doses of the AstraZeneca vaccine from Australia and 70,000 from India, but is not expected to get its first vaccine doses until at least next month.
In other developments across the world:
Prime Minister Boris Johnson of Britain on Tuesday defended the safety and efficacy of the AstraZeneca vaccine, which was produced with the University of Oxford. “That vaccine is safe and works extremely well,” he said in The Times of London, arguing that the nation’s inoculation campaign would bear fruits only if other countries had successful vaccine rollouts. “Successful as the U.K. vaccination program may be, there is little point in achieving some isolated national immunity.”
In France, the authorities identified a new variant of the coronavirus that does not appear to be deadlier or more contagious than other variants but that could be harder to detect with traditional testing. Eight cases of the variant were identified in a cluster of infections at a hospital in the western region of Brittany. Local health authorities said the variant was not “worrying” but would be closely monitored. Some of the people infected with the new variant cases had tested negative with a PCR nose swab, even though they had symptoms and more thorough testing showed that they had Covid-19.
Officials in France acknowledged that temporarily suspending use of the AstraZeneca vaccine would slow down the country’s vaccination campaign, but said that caution was necessary. Alain Fischer, an immunologist who heads the government’s vaccination advisory council, told France Inter radio on Tuesday that the suspension was a “hard blow” but that it was “reasonable to be cautious.”
More than two months into a campaign to give shots to troops and other essential residents at Guantánamo Bay, about one-third of the people who live at the remote naval station in Cuba have been fully vaccinated, according to Department of Defense figures.
The Pentagon has declined to say how many eligible troops and other residents at the outpost have declined the vaccine, or how many have received one dose but are not yet fully vaccinated. None of the wartime prisoners at the base have been vaccinated.
Guantánamo functions in some respects like a small town, with a K-12 school, church, community hospital and suburban-style neighborhoods for the families of Navy personnel and Pentagon contractors. There are about 5,100 adults residing at the base, including the 1,500 troops who serve at the prison on nine-month tours of duty, as well as about 400 children.
The military began vaccinating residents on Jan. 8 with the Moderna vaccine, starting with military medical personnel assigned to the prison and the hospital at the base. By Feb. 2, everyone who works at the prison, in or out of uniform, had been offered the vaccine, a prison spokesman said last month. Eligibility has been expanded to include hundreds of others, from commissary and airport workers to Navy officers and workers assigned to the war crimes court at the base, which has been closed through nearly the whole pandemic.
Lt. Col. Kenneth L. Hoffman of the Air Force, a Pentagon spokesman, said on Tuesday that as of March 12, a total of 3,200 people at the base were eligible, and 58 percent of them had been fully vaccinated — equivalent to about one-third of the base’s total population.
Spot testing, a 14-day quarantine for new arrivals and other measures have managed to prevent the virus from spreading at the isolated base. But the military cannot require troops to get a Covid vaccine, as it can with other immunizations, because the Covid shots are being given under an emergency use authorization.
Across the military, roughly one-third of active duty or National Guard troops have said no to the vaccines, particularly younger troops. The Pentagon has declined to describe the extent of refusals at Guantánamo.
The issue of vaccinating the 40 wartime prisoners held at Guantánamo has stirred some controversy. A Pentagon health official decided on Jan. 27 that the prisoners should be offered vaccination once all the troops at the base who wanted to be inoculated had a first dose. But the idea was put on hold after a public and political outcry, and there is currently no plan to vaccinate the prisoners, who range in age from the 30s to 73.
The coronavirus has been a major obstacle to resuming pretrial hearings in the prosecution related to the Sept. 11 terror attacks, in part because almost everyone involved other than the defendants travels to the court from across the United States.
Three prisoners charged with links to a terror cell in Southeast Asia were due for court appearances in February, their first in 17 years of detention, but an Army judge postponed the hearing until the summer, citing a lack of vaccinations and the risk of traveling during the pandemic.
A German children’s book on the coronavirus was removed from bookstore shelves after Chinese diplomats complained to the publisher about a passage on the virus’s origins.
In the book — which was written to explain the pandemic, lockdown measures and hygiene rules to children — Moritz, an elementary-school boy says, “The virus comes from China and has spread from there around the world.”
The Chinese Consul General of Hamburg made a complaint about the book to the district attorney’s office, according to a semiofficial Chinese news blog, German-China.
“With the malicious claim that the coronavirus originated in China, a German children’s book has caused outrage in the Chinese community in Germany,” the blog’s authors wrote.
In the past year, the Chinese state has tried to gloss over the provenance of the virus in favor of how well China has dealt with its outbreaks. Early in the pandemic, a title page in the newsmagazine Der Spiegel with the phrase “Coronavirus Made in China” caused outrage among Chinese diplomats.
Although research made public late last year indicated that the virus may have infected people in the United States and elsewhere earlier than previously thought, researchers still believe that it probably first began circulating in China.
Carlsen, the Hamburg-based publisher of the children’s book, said that the book had been written last spring, and that if writing it today, they wouldn’t have phrased the information quite the same way.
“Today we would not use this formulation, which has proved to have a far more ambiguous meaning than we intended,” Katrin Hogrebe, a spokeswoman for the publisher, said in a statement.
The sentence in question does not appear in a new edition of the book.
With Covid-19 deaths rising to their highest levels yet and a dangerous new virus variant stalking Brazil, the nation’s communications minister went to Beijing, where he met with Huawei executives and made an unusual request.
“I took advantage of the trip to ask for vaccines,” said the minister, Fábio Faria, recounting his meeting with Huawei, the telecommunications giant, last month.
Two weeks later, the Brazilian government announced the rules for its 5G wireless network auction, one of the biggest in the world. Huawei, which the government appeared to have barred just months before, would be allowed to participate.
The about-face is a sign of how politics in the region have been scrambled by the pandemic and President Donald Trump’s departure from the White House — and how China has begun to turn the tide.
China spent months batting away resentment and distrust as the place where the pandemic began, but in recent weeks its diplomats, pharmaceutical executives and other power brokers have been fielding scores of requests for vaccines from officials in Latin America.
Beijing’s ability to mass-produce vaccines and ship them to countries in the developing world — while rich countries like the United States are holding many millions of doses for themselves — has offered a diplomatic and public relations opening that China has seized.
Suddenly, Beijing finds itself with enormous leverage in Latin America, a region where it has a vast web of investments and ambitions to expand trade, military partnerships and cultural ties.
The precise connection between the vaccine request and Huawei’s inclusion in the 5G auction is unclear, but the timing is striking, and it is part of a stark change in Brazil’s stance toward China. The president, his son and the foreign minister stopped criticizing China, while cabinet officials with inroads to the Chinese, like Mr. Faria, worked furiously to get new vaccine shipments approved. Millions of doses have arrived in recent weeks.
As people across the United States jockey and wait to get vaccinated, a different problem is unfolding in the Cherokee Nation: plenty of shots, but not enough arms.
It is a side effect of early success, tribal health officials said. With many enthusiastic patients inoculated and new coronavirus infections at an ebb, the urgency for vaccines has gone quiet.
Now, the tribe is confronting what looms as a hurdle for the whole country as vaccine supplies swell to meet demand: how to vaccinate people who are not eagerly lined up for a shot.
That public health challenge encompasses persuading skeptics, calling people who don’t realize they are eligible, and making vaccines accessible for homebound patients, overstretched working families and people in rural areas and minority communities.
The Cherokee Nation has administered more than 33,000 doses at nine vaccination sites across its reservation, which spreads from cities through rural woodlands, cattle pastures and poultry farms in northeastern Oklahoma. After vaccinating health care workers, Cherokee-speaking elders and essential workers, the tribe opened appointments to anyone who qualifies, tribal member or not, living in its borders.
Still, hundreds of slots have gone unfilled, health officials said. Cherokee-speaking vaccine schedulers hired to set up appointments are waiting for their phones to ring.
The Osage Nation, in northeastern Oklahoma, is vaccinating about 200 people a day at a clinic that has the capacity to give 500 shots. It tried two mass vaccination events at its casinos, but the results were disappointing.
So the tribe bought two 30-foot “medical RVs” that will roll into smaller towns like Hominy and Fairfax to reach the 30 to 40 percent of tribal elders and essential workers who did not volunteer to get vaccinated. It is a house-by-house campaign against misinformation and wariness, waged with long conversations and patience.
“We tried to remove every obstacle to people who were sitting on the fence,” said Dr. Ronald Shaw, the medical director of the Osage Nation.
As President Biden pushes to vaccinate as many Americans as possible, he faces deep skepticism among many Republicans, a group especially challenging for him to persuade.
While there are degrees of opposition to vaccination for Covid-19 among a number of groups, including African-Americans and antivaccine activists, polling suggests that opinions in this case are breaking substantially along partisan lines.
A third of Republicans said in a CBS News poll that they would not be vaccinated — compared with 10 percent of Democrats — and another 20 percent of Republicans said they were unsure. Other polls have found similar trends.
With the Biden administration readying television and internet advertising and other efforts to promote vaccination, the challenge for the White House is complicated by perceptions of former President Donald J. Trump’s stance on the issue. Although Mr. Trump was vaccinated before he left office and urged conservatives last month to get inoculated, many of his supporters appear reluctant to do so, and he has not played any prominent role in promoting vaccination.
Asked about the issue on Monday at the White House, Mr. Biden said Mr. Trump’s help promoting vaccination was less important than getting trusted community figures on board.
“I discussed it with my team, and they say the thing that has more impact than anything Trump would say to the MAGA folks is what the local doctor, what the local preachers, what the local people in the community say,” Mr. Biden said, referring to Mr. Trump’s supporters and campaign slogan “Make America Great Again.”
Widespread opposition to vaccination, if not overcome, could slow the United States from reaching the point where the virus can no longer spread easily, setting back efforts to get the economy humming again and people back to a more normal life. While the problem until now has been access to relatively tight supplies of the vaccine, administration officials expect to soon face the possibility of supply exceeding demand if many Americans remain reluctant.
Chinese embassies in a rapidly growing number of countries, including the United States, have begun requiring that foreigners entering China must first be fully inoculated with a Chinese-made coronavirus vaccine if they want to avoid extensive paperwork requirements.
Complying with the rule will be difficult for people applying for Chinese visas in places that are not offering vaccines produced in China. No Chinese-made vaccine has been approved in the United States or most of Europe.
Many regulators outside China have been wary of vaccines made by companies in China, notably Sinovac and Sinopharm. The companies have released relatively little data from Phase 3 trials to allow independent assessments of the vaccines’ efficacy and safety.
The Chinese Foreign Ministry announced similar rules for foreigners wanting to enter the Chinese mainland from Hong Kong. It said on Saturday that if they received a Chinese-made vaccine they would not need to meet other requirements, including a negative nucleic acid test, detailed health and travel records, and a personal invitation from a Chinese provincial government agency.
Some foreigners who live and work in the Chinese mainland but left early in the pandemic have been living in limbo for a year or more in Hong Kong, which has authorized the Sinovac and BioNTech vaccines, and elsewhere.
By Tuesday morning, Chinese embassies had issued identical rules in Britain, Japan, Norway, Pakistan, the Philippines, Thailand, the United States, Vietnam and at least a dozen other countries.
The Chinese stance puts pressure on other countries to give regulatory approval to China’s vaccines. Beijing has not allowed vaccines developed in other countries to be produced or administered in China.
Thousands of businesspeople and students have been seeking visas to resume their work or studies in China. The country’s borders have been among the most tightly closed in the world to prevent the coronavirus from re-entering the country after being largely stamped out. Business leaders say the new vaccine recommendation adds to the hurdles.
The N.C.A.A. quietly rewrote part of its coronavirus safety protocols, which college sports administrators have routinely used to justify holding basketball championships during the pandemic, to potentially shorten the quarantines of some teams arriving in Indiana for the Division I men’s tournament.
The association’s published health guidelines, which also apply to the women’s tournament scheduled to begin next week in Texas, call for teams to “remain in quarantine until two consecutive tests on separate days are confirmed negative, at which time team practice may begin.” But the N.C.A.A.’s unannounced change offers teams arriving late at night a quicker way out: negative results on virus tests separated by at least 12 hours.
The shift, acknowledged only after inquiries from The New York Times, allowed Iona, the No. 15 seed in the East region, to practice less than 24 hours after its chartered plane landed in Indianapolis late in the night it clinched its automatic bid.
The episode involving Iona, which Coach Rick Pitino steered to a victory in the Metro Atlantic Athletic Conference tournament on Saturday, is an early signal of how the N.C.A.A. may interpret, apply and change the safety rules it is relying on to stage 67 games in Indiana over the coming weeks.
Like their counterparts in many leagues, college sports administrators routinely recalibrated their approach to the pandemic, not just in details but sometimes with respect to issues they had depicted as foundational principles. Last year, for instance, executives regularly said that college games would not happen unless students were on campuses for classes — a position that ultimately faded away as the fall football season approached.
In statements on Monday, the N.C.A.A. said its medical advisers and public health officials had decided to allow teams that arrived late at night to leave quarantine after clearing two polymerase chain reaction tests, which are considered to be the gold standard in infectious disease diagnostics, that were administered at least 12 hours apart. And no matter when they arrive, players and coaches, as long planned, must also record seven straight days of negative tests before traveling to Indiana or Texas.
The association did not immediately say when it had changed its quarantine policy or why its published guidelines did not include an exception to it, but the modification was in place by the time Iona landed in Indianapolis, a school official said. In a separate interview on Monday, Mark Emmert, the N.C.A.A. president, said that while the association’s health rules could evolve, its central intent would not.
Although Pitino has often run afoul of N.C.A.A. rules over his long career, there is no indication that Iona, which is scheduled to play No. 2 Alabama on Saturday, held a surreptitious practice without the consent of tournament organizers.
The N.C.A.A.’s ambitious plan to host the men’s basketball tournament, an event more crucial than any other to the association’s finances, has been under scrutiny for months, and some public health experts have sharply questioned the decision to allow spectators.
After a report by Stadium, the N.C.A.A. acknowledged late Monday that six officials would not work at the men’s tournament as planned because one had tested positive for the virus and others had been found to have had “prolonged close contact.” Although the N.C.A.A. said it would use four substitute officials, it said that two referees would not be replaced.
In recent days, the association has also grappled with whether two of college basketball’s most prominent programs, Kansas and Virginia, should play in the tournament despite recent virus cases.