The end of the emergency will bring about a host of policy changes, and it signals a new chapter in the government’s pandemic response.WASHINGTON — The Biden administration plans to let the coronavirus public health emergency expire in May, the White House said on Monday, a sign that federal officials believe the pandemic has moved into a new, less dire phase.The White House wants to keep the emergency in place for several more months so hospitals, health providers and health officials can prepare for a host of changes that will come when it ends, officials said. Millions of Americans have received free Covid tests, treatments and vaccines during the pandemic, and not all of that will continue to be free once the emergency is declared over.An average of more than 500 Americans are still dying from Covid every day. But at the three-year mark, the coronavirus is no longer upending everyday life to the same extent, partly because much of the population has at least some protection against the virus from vaccinations and prior infections.Still, the White House said on Monday that the nation needed an orderly transition out of the public health emergency. The administration said it also intended to allow a separate declaration of a national emergency to expire in May.“An abrupt end to the emergency declarations would create wide-ranging chaos and uncertainty throughout the health care system — for states, for hospitals and doctors’ offices, and, most importantly, for tens of millions of Americans,” the White House said in a statement.

A top F.D.A. regulator said there was compelling data for redesigned coronavirus vaccines from Pfizer-BioNTech and Moderna.WASHINGTON — The Biden administration plans to offer the next generation of coronavirus booster shots to Americans 12 and older soon after Labor Day, a campaign that federal officials hope will reduce deaths from Covid-19 and protect against an expected winter surge.Dr. Peter Marks, the top vaccine regulator for the Food and Drug Administration, said in an interview on Tuesday that his team was close to authorizing updated doses that would target the versions of the virus now circulating.Even though those formulations have not been tested in humans, he said, the agency has “extremely good” data showing that the shots are safe and will be effective. “How confident am I?” he said. “I’m extremely confident.”This week, both Moderna and Pfizer-BioNTech finalized their submissions to the F.D.A. asking for emergency authorization of booster shots aimed at BA.5 and another subvariant of Omicron that together account for most coronavirus cases in the United States.Federal health officials say they are eager to offer the updated boosters as quickly as possible, pointing to a death toll that now averages about 450 Americans per day and could rise in the coming months as people spend more time indoors.“We have really got to do better to protect the American public,” Dr. Anthony S. Fauci, President Biden’s chief medical adviser, said in an interview on Tuesday. “We are in the middle of a BA.5 outbreak here, and we are nowhere near where we want to be.”The Biden administration has struggled to convince Americans of the need for successive vaccinations. Only about two-thirds of the population has been inoculated with the primary series of two shots, and far fewer have received booster doses.Some outside scientists have said the government is moving too fast to clear redesigned shots, saying that the existing vaccines provide strong protection against severe disease.“Deaths are concentrated in unvaccinated people and people with serious health conditions,” said John P. Moore, a virologist at Weill Cornell Medicine. He said the protection that the new shots provided against infection could be “weak to nonexistent.”Jeremy Kamil, a virologist at Louisiana State University Health Shreveport, said that although he supported new boosters, many people had immunity from recent infections. “Even if we get this out in the next 10 days, how many people are left who haven’t gotten Omicron?” he said.Read More on the Coronavirus PandemicNew Guidelines: The Centers for Disease Control and Prevention loosened its Covid-19 guidance, saying those exposed to the virus no longer need to quarantine.A Sweeping Rebuke: Dr. Rochelle P. Walensky, the director of the Centers for Disease Control and Prevention, said that her agency had failed to respond quickly enough to the coronavirus pandemic and needed to be overhauled.Back to School: New York City’s Education Department has rolled back most Covid restrictions ahead of the start of school on Sept. 8, reflecting a wider shift toward learning how to live with the virus.A Century-Old Vaccine: The results of clinical trials, launched in the early days of the pandemic, involving an old tuberculosis vaccine offered hope that it could provide a measure of universal protection against infectious diseases.Other scientists said that the government’s plan made sense given how the virus has changed. Dr. Marks said that if regulators waited for additional data or recommendations from outside experts, the virus might evolve further and “we may have lost a bunch of individuals who could otherwise be sitting around at the dinner table together.”In a sign of impending action from the F.D.A., the Centers for Disease Control and Prevention has scheduled a two-day meeting of its advisory panel of experts on the matter for Sept. 1 and 2. The C.D.C. director, Rochelle P. Walensky, would then make a final decision on whether to roll out the new doses. Shipments to states could begin as early as next week.Officials plan to offer the new Pfizer booster to everyone 12 and older while limiting the new Moderna shot to adults. People who have already received the initial two-shot series of either vaccine would be eligible. So would those who have received the initial shots plus one or two booster shots. The new booster campaign could be broadened to younger children later.Dr. Marks said the F.D.A. might want people who have recently received a Covid vaccine dose to wait “a few months” before getting the new shot. He said the C.D.C. might weigh in on whether people who were recently infected with the virus should also wait.As of mid-August, the federal government had bought more than 170 million doses of the updated version of the vaccines. This month, the C.D.C. laid out detailed plans to offer the shots, warning that the supply would be “sufficient but finite” and saying that doses should be “directed to providers with expected demand among eligible patients.”The new shots combine the original vaccine with components aimed at the BA.4 and BA.5, Omicron’s recent subvariants. Officials argue that the new formulations will deliver a stronger boost to the immune system than the existing vaccines provide.Unlike earlier shots, the redesigned formulations have not been tested widely on humans; instead, the companies have submitted data from mice trials. Some vaccine experts have complained that animal data is too preliminary and regulators should wait for results of trials with human volunteers.But Dr. Fauci said using such data was “not anything different than we always do” in updating the flu vaccine each year. And Dr. Marks said the evidence includes the existing vaccines’ extensive track record and a series of earlier human trials with variant-specific formulations.“I take great issue with those who say, ‘Oh, you’re just approving this with mouse data,’” he said. “We’re authorizing this with the totality of the evidence that we have.”Moderna and Pfizer have both submitted clinical data from human studies of redesigned shots targeting the original version of the Omicron variant. Britain last week authorized that version of Moderna’s vaccine, but U.S. regulators asked for formulations aimed at the newer subvariants.Researchers are still working to answer key questions about the protection that the new vaccines deliver, including the levels of antibodies the shots generate in humans and how those antibodies protect people. Moderna began human trials of its new vaccine this month, and Pfizer plans to do the same later in the month. Initial data from those trials is expected later this year.Federal regulators are reviewing applications from Moderna and Pfizer-BioNTech for emergency authorization of new booster shots that target Omicron subvariants now circulating.Kenny Holston for The New York TimesDr. Moore, the virologist at Weill Cornell Medicine, said the administration’s plans could backfire if the fall or winter brings a wave of disease despite the new formulations, potentially reducing overall confidence in Covid-19 vaccines.“My issue all along has been: Is there enough data to really justify the effort?” Dr. Moore said. “The potential downside is, if the public thinks that this Omicron-containing booster is some kind of magic bullet that will give them super strong protection from infection, is there a risk that they will change their behavior to increase their exposure?”The F.D.A. will decide whether to authorize the retooled doses without seeking a recommendation from its outside advisory panel of experts, a step it usually takes before making new vaccines available. Critics have complained that regulators have bypassed the panel at crucial steps.Dr. Marks defended the decision, saying a late June meeting of the advisory panel on the need to update the vaccines had given regulators “everything we needed.” The committee voted overwhelming then to recommend that the vaccines be updated for Omicron, but it did not consider specific formulations.

The approach — injecting one-fifth of the current dose into the skin instead of a full dose into underlying fat — would help stretch out the nation’s limited supply of vaccine.WASHINGTON — The Biden administration has decided to stretch out its limited supply of monkeypox vaccine by allowing a different method of injection that uses one-fifth as much per shot, according to senior administration officials familiar with the planning.In order for the Food and Drug Administration to authorize so-called intradermal injection, which would involve injecting one-fifth of the current dose into the skin instead of a full dose into underlying fat, the Department of Health and Human Services will need to issue a new emergency declaration allowing regulators to invoke the F.D.A.’s emergency use powers. That declaration is expected as early as Tuesday afternoon.The move would help alleviate a shortage of vaccine that has turned into a growing political and public health problem for the administration. The administration has faced a barrage of criticism that it was too slow to ship vaccine that was ready for use to the United States from Denmark, where it was manufactured, and too slow to order that bulk vaccine stocks be processed into vials after the disease first surfaced here in mid-May.In less than three months, more than 8,900 monkeypox cases have been reported. The disease spreads primarily through skin-to-skin contact during sex among gay and bisexual men. Federal officials are concerned about both the current infection rate and the risk that the disease could spread to other parts of the population.What to Know About the Monkeypox VirusCard 1 of 7What is monkeypox?

A new way of injecting monkeypox vaccine could stretch the nation’s supply of shots, but some experts argue that the approach has not been sufficiently studied.WASHINGTON — It sounded like a simple solution to the shortage of monkeypox vaccine: Merely by changing the way doses are injected, the federal government could vaccinate five times as many people with the supply it has in hand.But the approach — injecting one-fifth of the current dose into the skin instead of a full dose into underlying fat — is not actually all that simple, experts say. And some federal officials are concerned about changing the method without more research, even though Dr. Robert M. Califf, the head of the Food and Drug Administration, described the proposal on Thursday as promising.Some outside experts, too, are urging caution. “From a basic science perspective, this should work,” said Dr. Jay K. Varma, the director of the Cornell Center for Pandemic Prevention and Response. “But, of course, there are lots of things in life, in science, that we think should work, and then when we actually do them, they don’t.”Stretching out doses of the vaccine, Jynneos, could help the federal government resolve a predicament partly of its own making. Even though it invested more than $1 billion developing the two-dose vaccine that to use against both monkeypox and smallpox, the government only has 1.1 million shots on hand, partly because it was slow to order bulk vaccine stocks to be processed into vials.That supply is enough to cover 550,000 people, but about three times as many doses are needed to cover the 1.6 million to 1.7 million Americans who, according to the Centers for Disease Control and Prevention, are at high risk of monkeypox. For now, the virus has been spreading primarily through skin-to-skin contact during sex among gay and bisexual men, the C.D.C. has said.Some federal officials are hoping that by injecting a smaller dose of the vaccine between skin layers, called an intradermal shot, the Biden administration could tamp down the outbreak before it spreads more widely.But some experts argue that this approach has not been sufficiently studied. They also warn that some vaccinators will need training to properly deliver the shots, which could slow vaccination efforts. Otherwise, the government could end up wasting doses, not saving them.Intradermal injection involves carefully guiding a needle into skin layers, a thin space with immune cells. If a vaccinator goes too deep and inserts the dose into fat, the patient might not receive enough vaccine, experts say. But if the needle is not inserted far enough, some of the vaccine could leak back out.“If you’re giving a lower dose and you don’t inject it properly into the skin — you might inject it into the wrong place — you may not be giving a protective vaccine,” said Dr. Phil Krause, who retired as a senior F.D.A. vaccine regulator last year and worked on the agency’s licensing of Jynneos. “If you ask this to be done nationwide in millions of doses, it’s a lot easier for there to be mistakes made in the administration of the vaccine.”On the other hand, the method has a track record. It has been used in polio vaccination campaigns when doses have been limited, as well as for rabies and for tuberculosis skin tests.What to Know About the Monkeypox VirusCard 1 of 7What is monkeypox?

States have already ordered millions of doses; if the agency authorizes them in the coming days, babies, toddlers and preschoolers could start receiving shots next week.WASHINGTON — The only Americans still not eligible for coronavirus vaccines — babies, toddlers and preschoolers — appear on the verge of finally getting cleared to receive them after an advisory panel to the Food and Drug Administration voted unanimously on Wednesday to recommend the Pfizer and Moderna vaccines for the group.The F.D.A. appears poised to authorize Moderna’s vaccine for children younger than 6 and Pfizer’s for those younger than 5 as soon as Friday. States have already ordered millions of doses, and White House officials have said shots could roll out as early as next week.The committee’s 21-0 votes came after a daylong review of clinical trial data and signaled the end of a process that involved months of false starts and dashed hopes for a vaccine to cover the youngest Americans. Except for the roughly 20 million children under 5, everyone has had access to coronavirus shots for many months and is eligible now for booster shots.The F.D.A. and the Centers for Disease Control and Prevention jointly made a strong push for a positive recommendation, showering the committee with 230 pages of data that they said showed the vaccines were safe and provoked a strong immune response in children. Regulators also emphasized that even though young children are generally at low risk for serious illness from the virus, vaccinating the group would save lives.“We have to be careful that we don’t become numb to the number of pediatric deaths because of the overwhelming number of older deaths here,” Dr. Peter Marks, the F.D.A.’s top vaccine regulator said. “The intervention we’re talking about here is one that is something that we have accepted in the past to try to prevent deaths from influenza,” he added.Officials from the C.D.C. said that more than half of young children hospitalized with Covid had no underlying medical conditions. During the Omicron wave in the winter, young children were hospitalized at a higher rate than older children and adolescents, and their illness tended to be at least as severe. More than 200 children aged 6 months through 4 years old have died of Covid, according to death certificate data that is one of the most conservative estimates.The panel members, some of whom have treated hospitalized children for Covid and have comforted terrified parents, seemed eager to act.“There are so many parents who are absolutely desperate to get this vaccine,” said Dr. Jay Portnoy, a professor of pediatrics at the University of Missouri-Kansas City medical school. “I think we owe it to them to give them the choice.”Dr. Arthur Reingold, an epidemiologist at the University of California, Berkeley, School of Public Health, said the nation already vaccinates children against diseases “where the risk of a child dying or being hospitalized of those diseases was pretty close to zero.”The C.D.C.’s own panel of vaccine experts is set to take up the matter over two days this weekend. If that committee also gives a favorable recommendation, Dr. Rochelle P. Walensky, the agency’s director, would issue her decision, the final step in the process.Neither vaccine has been tested against new subvariants that are circulating in the United States. The clinical trials were largely conducted when the Omicron variant prevailed. Two subvariants, BA.4 and BA.5, could become dominant within a month.The virus is evolving so fast that some panelists expressed fear that the clinical trial results on which their decisions were based were already outdated. “We’re really trying to predict the future,” Dr. Paul Offit, a vaccine expert with the Children’s Hospital of Philadelphia and an F.D.A. panelist, said in an interview. “This is a problem.”But the panel’s biggest worry seemed to be whether Pfizer’s three-dose vaccine, which it developed with its German partner, BioNTech, was effective enough. Pfizer has reported that two doses of its vaccine were only about 28 percent effective in preventing symptomatic disease; Dr. Susan Wollersheim, an F.D.A. reviewer, said the company’s data did not clearly show that two doses drove down the incidence of Covid.Pfizer argued that three doses were 80 percent effective, but the finding was based on only 10 cases out of a subset of 1,678 trial participants. Dr. Doran Fink, a senior F.D.A. vaccine regulator, cast doubt on the company’s estimate, describing it as “preliminary” and “imprecise.”He said the F.D.A. was “very confident” from the immune response data that Pfizer’s vaccine, like Moderna’s, met the criteria for emergency use authorization, which requires that benefits outweigh risks. But some panel members were clearly worried that parents might be misled.Dr. Amanda Cohn, a top C.D.C. official and panel member, said she did not have “any idea” what the efficacy rate after three doses of Pfizer will end up being, and that officials should not embrace the 80 percent estimate.Jeannette Y. Lee, a biostatistician at the University of Arkansas for Medical Sciences, raised another concern: that some parents might skip the crucial third dose for their children. “As we know, it’s a struggle to get people in for two,” she said.Pfizer officials said the data showed the vaccine’s effectiveness built over time. “It’s not as if there’s no efficacy at all,” Dr. William C. Gruber, a senior vice president at Pfizer, said.For some parents, the bar is low. Some of the more than 1,600 parents who responded a New York Times query about life with an unvaccinated young child said they would accept any efficacy above zero to give their children some protection.“To keep her safe from illness and potential death or lifelong hardship? Why is this a question?” wrote Cayla Miller, a mother in Swanville, Maine. “We’ve been waiting so long to protect our whole family. I’ve nearly lost my job and my mind trying to keep her safe.”Scientists and federal officials have warned against directly comparing the Moderna and Pfizer vaccines. Not only did the companies conduct their clinical trials at different times, with different populations, but the dosing and regimens differ.Pfizer has proposed a three-dose regimen at one-tenth the strength of its adult dosage, with the first two doses spaced by three weeks and the third at least two months after the second. Moderna wants to offer two doses of vaccine, four weeks apart, at one-fourth the strength of its adult dose. Moderna’s adult dose is significantly stronger than Pfizer’s.Dr. Wollersheim of the F.D.A. declined to answer when one panelist asked for a comparison of the vaccines’ effectiveness in young children. But as some parents will likely do, some panel members tried to do their own matchup.Dr. Offit noted that Moderna’s efficacy data was somewhat stronger than Pfizer’s: about 51 percent effective in preventing symptomatic infection in children 6 months to 2 years old and 37 percent effective in children 2 through 5.Even though protection against symptomatic infection was limited, he said, it was possible to predict that Moderna’s vaccine would ward off severe disease.“I’m not so sure you can predict that with Pfizer’s vaccine,” he said. “I fear that they may have under dosed.”Both vaccines provoked levels of neutralizing, or virus-blocking, antibodies among children comparable to those in younger adults. Pfizer’s vaccine has been authorized for children 5 to 15 since last year, and regulators said it helped prevent hospitalization and deaths.Still, both appear significantly less effective against symptomatic infection than the adult vaccines when they were introduced 18 months ago. The F.D.A. said that was because Omicron proved far more adept at evading the vaccines’ defenses against infection than previous versions of the virus.Given evidence of waning potency over time, the FD.A. has said that young children who get Pfizer and Moderna shots will likely require booster shots, just as older recipients have. That would mean Pfizer’s vaccine could wind up as four doses, while Moderna’s could be three.Neither vaccine provoked serious safety concerns. The vast majority of side effects were mild — irritability and crying, sleepiness, fatigue and loss of appetite. Recipients of Moderna’s vaccine appeared more likely to experience fevers, but in line with those provoked by other pediatric vaccines, the F.D.A. said.Federal health officials have said they expect many children under 5 to be vaccinated by pediatricians and primary care physicians, a contrast to older age groups. But the uptake is expected to be low; children aged 5 to 11 became eligible to be vaccinated late last year, but only about 37 percent of them have gotten at least one dose.Doses are packaged by the hundred to reach smaller practices and rural locations. The Biden administration has also advertised a network of other locations that would work to reach families, including pharmacies and children’s hospitals, while groups such the Association of Children’s Museums and the National Diaper Bank Network will help with education efforts.One topic of discussion among the F.D.A. panel members was how to address the many parents whose children already have acquired some natural immunity. Federal health officials presented data to the committee this week suggesting that more than two-thirds of children aged 1 to 4 years old have already been infected with the virus.A Moderna official told the committee that the company’s trial found that young children who had gotten the virus and were vaccinated had greater levels of protection, a conclusion backed by outside research.Dr. James E.K. Hildreth, a committee member and the president of Meharry Medical College in Nashville, noted that many children had been infected “and have done just fine.”“But for those parents who choose to do so, especially for those parents of kids with underlying conditions,” he added, “this is a choice they should have.”Emily Erdos

Moderna is going head-to-head with Pfizer-BioNTech for the opportunity to vaccinate the youngest children, the only Americans still not eligible for shots.WASHINGTON — Over the past 10 months, as tens of millions of children and teenagers received the Pfizer-BioNTech vaccine, the companies’ main rival, Moderna, sat on the sidelines, its shot limited to adults.But Moderna may now be poised for a comeback at a critical juncture in the nation’s vaccination campaign. The company is expected to send federal officials initial data this week on how well its coronavirus vaccine works for the nation’s youngest children.About 18 million children under the age of 5 are the only Americans not yet eligible for vaccination. And while uptake for older children has been slow, many parents are still anxiously awaiting the chance to protect their babies, toddlers and preschoolers.Moderna is going head-to-head with Pfizer-BioNTech for the opportunity to vaccinate this group, hoping it has found what some scientists are calling the “Goldilocks” dose: strong enough to offer lasting protection, but not so strong that it causes widespread worrisome side effects, such as high fevers.Moderna has opted for a regimen of two doses at a quarter the strength of its adult dose for children under 6. Pfizer is expected to seek authorization next month for a three-shot regimen for children under 5, with doses one-tenth as strong as those for people aged 12 and up.Moderna is also expected to release data soon from its clinical trial on the next age group up: children aged 6 to 11.Dr. Yvonne Maldonado, a Stanford professor of pediatric infectious diseases and a lead investigator at the Stanford site of Pfizer’s pediatric vaccine trials, said new data from both Moderna and BioNTech in the coming weeks will offer critical insight into the effectiveness of their pediatric shots. She said researchers are watching carefully to see if Moderna’s stronger doses “result in more robust immune responses” than Pfizer’s shots have elicited in young children.A series of new studies raising questions about how long Pfizer’s lower doses protect elementary-school-age children has piqued interest among federal scientists and vaccine experts in Moderna’s choices.Dr. Ofer Levy, a pediatric expert at Harvard Medical School and a member of the Food and Drug Administration’s independent vaccine advisory committee, said he thought Pfizer might have selected too low a dose for 5- to 11-year-olds “in the understandable priority to maximize safety.”To date, Pfizer has been the only player in vaccinating younger Americans, winning authorization to vaccinate 12- to 15-year-olds last May, followed by 5- to 11-year-olds in October. Its authorization for adults also covers 16- and 17-year-olds.Moderna sought authorization to vaccinate teenagers last June, but the F.D.A. delayed considering the request because of concerns about the risk of myocarditis, a condition involving inflammation of the heart that has been tied to both the Moderna and the Pfizer shots.More than 22 million people in the United States under 18 are now fully vaccinated with the Pfizer vaccine, but uptake has been leveling off. Only roughly one in four children ages 5 to 11 are fully vaccinated, for example, even though shots have been offered to that group for more than four months.But there is still a demand to protect the youngest children as more of the country unmasks, more parents return to workplaces and the summer travel season approaches.Compared with adults, “there is no question that in children the benefit of an effective vaccine is less, because fewer get really sick,” said Dr. Eric Rubin, an infectious disease expert at the Harvard T.H. Chan School of Public Health and a member of an advisory panel to the Food and Drug Administration.“But it will benefit some individuals,” he said. “It will save some lives.” According to the Centers for Disease Control and Prevention, 336 children in the United States under the age of 5 have died of Covid since the start of the pandemic.Doses of the Pfizer children’s vaccine being prepared in Abuquerque in November. Pfizer and Moderna are testing different doses for children, compared to their adult vaccines.Paul Ratje for The New York TimesHopes that the youngest children would soon be covered surged last month after regulators pressed Pfizer-BioNTech to submit preliminary results from its three-dose trial. The F.D.A. wanted to get the vaccination campaign underway with two doses while awaiting final results on three.But that effort collapsed when new data from Pfizer that encompassed more of the Omicron surge showed convincingly that two doses failed to protect adequately against symptomatic infection. Now, more detailed results from Pfizer’s and Moderna’s trials are materializing at roughly the same time. And while neither company knows yet whether its vaccines will prove effective enough for the youngest age group, but both say their research shows they are safe.“We have not seen anything untoward right now, so we feel confident in the safety profile,” Dr. Paul Burton, Moderna’s chief medical officer, said in an interview.Amy Rose, Pfizer’s spokeswoman, has said that after careful research, Pfizer-BioNTech chose the “safest and most tolerable dose” for young children. The companies have said they are hopeful that a three-shot regimen will provide strong protection for children under the age of 5. Pfizer is testing a 10-microgram dose for 5- to 11-year-olds, a third of the adult and teenage dosing; and 3 micrograms for children under 5.Moderna is proposing substantially higher dosing than Pfizer in all three pediatric age groups: 100 micrograms, the full adult dose, for those ages 12 to 17; 50 micrograms in children 6 to 11, and 25 micrograms in those under 6. Regulators are considered likely to review the firm’s data for all three age groups simultaneously.“We really stand behind those doses,” Dr. Burton said. Although federal officials say both Pfizer and Moderna’s vaccines wane in potency over time, some studies of adults have suggested that Moderna’s protection holds up longer. “I think it comes down to dose,” Dr. Burton said.He said initial results showed a 50-microgram Moderna dose prompted a “robust immune response” in children 6 to 11. While the overall number of infections was small, researchers hope that trial will help reveal how well the vaccine prevents illness, not just how high it boosts antibody levels.Dr. Philip Krause, who recently retired as a senior vaccine regulator at the F.D.A., said the agency spent significant time last year worrying about the safety of Moderna’s vaccine for those under 18, with some studies showing a higher risk of myocarditis from the company’s shot than from Pfizer’s.“The question is always: What is the dose that gives rise to an immune response that we think is likely to be protective?” he said. “You couldn’t actually test to figure out the rate of myocarditis since it’s rare, but you could ask, ‘What are we sacrificing in immune response by lowering the dose, and do we think that’s important?’”Preschoolers wearing masks in Annandale, Va., last year. As precautions are lifted in states, there is still interest in protecting the youngest children who are not eligible for vaccines.Cheriss May for The New York TimesPartly because of concerns about myocarditis, the C.D.C. recently encouraged some people 12 or older, particularly boys and men between 12 and 39, to wait eight weeks between their first and second Pfizer or Moderna shots. Studies have shown that teenage boys and young men are most at risk of developing the side effect.Dr. Burton said that overall the research had proved reassuring, including recent British data that showed myocarditis was very rare and typically mild in both Pfizer and Moderna recipients. But Dr. Walid F. Gellad, a drug safety expert at the University of Pittsburgh, said it remained unclear whether Moderna’s higher dosing might elevate the risk of myocarditis in young children. The company’s pediatric studies are most likely much too small to identify the risk of the side effect, he and other experts said.Moderna’s new push also comes after several studies raised questions about the protection that two doses of Pfizer-BioNTech’s vaccine provide for children 5 to 11. Researchers in New York State’s health department recently found that protection against infection from two doses faded significantly within weeks. C.D.C. researchers separately found that during the Omicron wave, the effectiveness of two doses of the Pfizer shot against moderate forms of the disease in children ages 5 to 11 dropped significantly.The studies have kindled a debate among vaccine experts about whether a stronger dose would have been better or whether those children need third doses. Booster shots are now authorized for everyone 12 and up. Pfizer expects results from its study of a three-dose regimen for the younger children next month.Dr. Gellad said it was possible the Pfizer dose for 5- to 11-year-olds may have been too weak, but that scientists could not yet be certain. He said he expected regulators would be especially careful in considering higher doses for young children given the comparatively low risks of them catching Covid now and getting severely ill.Amid all the questions, one thing is clear: The back and forth over which vaccine will be better for young children could discourage uptake.Alison M. Buttenheim, a behavioral health expert at the University of Pennsylvania, said those considering vaccination found comfort in certainty. Otherwise, “that’s just going to pave the way to say, ‘I’m going to hold off,’” she said. “A lot of people are uncomfortable with evolving science.”

The agency will wait for data on whether three doses of Pfizer-BioNTech’s Covid vaccine are effective in young children after new, disappointing data.WASHINGTON — In a striking reversal, federal regulators said on Friday that they would wait for data on how well three doses of Pfizer-BioNTech’s coronavirus vaccine work in children younger than 5 before deciding whether to authorize the vaccine for that age group.The decision by the Food and Drug Administration most likely rules out shots for roughly 18 million of the nation’s youngest children until at least April. The Biden administration had been hoping to expand vaccination to those 6 months through 4 years of age as early as next week. They are the only Americans not yet eligible for shots.Pfizer-BioNTech asked for the delay after the companies discovered that the Omicron wave had led to a far higher rate of infection than they had previously recorded among young volunteers in their clinical trial. The new data underscored that the Omicron variant was better than the earlier Delta variant at evading the vaccine’s protection, and it showed that two doses, which had already fallen short by another measure, were not effective enough.As a result, the companies and the F.D.A. agreed to wait for the results from a third dose, which are expected in early April.The turnabout came as the Centers for Disease Control and Prevention released data on Friday showing that booster shots of the Pfizer and Moderna vaccines lose some of their effectiveness against emergency room visits and hospitalizations by the four-month point. The agency said the data was some of earliest evidence on the durability of boosters. While it showed three doses offered better protection than two, it raised sobering questions about how long that protection lasts against severe disease.Together, the two developments dampened some earlier optimism about vaccines. They also presented at least a temporary setback for the Biden administration’s vaccination campaign.Researchers hope that by April, Pfizer and BioNTech will be able to demonstrate that three doses protect children, with data showing both stronger immune responses and more success in warding off symptomatic infections.The companies said in a news release that they would wait for the data on a three-dose vaccine given the study’s rapid pace and because they “continue to believe it may provide a higher level of protection in this age group.”The F.D.A. began pressing Pfizer-BioNTech to seek authorization for a two-shot regimen weeks ago, despite disappointing results from the trial that were announced in December. Children ages 2 through 4 produced only 60 percent of the antibody levels that older teens and young adults did. The older age group was used as a benchmark because the vaccine had proven effective for them.Children 6 months to 2 years did produce the sought-after level of antibodies. The dosage was one-tenth of that given to those 12 and older, and there were no serious safety concerns, officials have said.This month, Pfizer-BioNTech submitted a request for emergency authorization, and the F.D.A. scheduled a meeting of its outside advisory committee for next Tuesday, saying it hoped to get a head start on vaccinating young children with two shots, likely adding a third later.Then, late on Thursday, Pfizer alerted the F.D.A. that it had more recent data, from mid-January on, showing a more discouraging picture as the Omicron variant bore down. The new data revealed that two doses were not sufficiently effective in preventing symptomatic infection. The illness was generally mild and no children were hospitalized, according to people familiar with the study.In a call with reporters on Friday, Dr. Peter Marks, the F.D.A.’s top vaccine regulator and an advocate of the two-dose strategy, said the latest data had forced a new reckoning. “Yes, some of this was late breaking,” he said, “but that’s what our job is — to adjust to it.”While many pediatric experts had been sympathetic to the F.D.A.’s initial push to consider two doses, some said on Friday that the regulators were right to hold off.“I honestly let out a woo-hoo of elation that reason and science had prevailed, and that they actually really did do the right thing,” said Dr. James Conway, a pediatric infectious disease expert at the University of Wisconsin-Madison and a fellow of the American Academy of Pediatrics.Dr. Conway said he had been concerned that prematurely authorizing a partial vaccine regimen for young children without compelling data would have intensified suspicion among some Americans that the federal government had cut corners.Norman W. Baylor, a former director of the F.D.A.’s vaccines office, said the agency had been “reactionary” on a highly delicate issue, perhaps because of public pressure. A lot of parents, he noted, had been saying, “I don’t care, just give my kid the two doses and even if it’s a little bit and they’re not protected fully, that’ll do the trick.”“But we don’t know that until the data are reviewed,” he said.Dr. Baylor and some other experts questioned whether any coronavirus vaccine developer had yet figured out an effective dose for the youngest children, or how durable protection would be for them. Moderna, the other major vaccine manufacturer, is currently testing a stronger dose than Pfizer’s for children under 5. But so far, Moderna’s vaccine has only been authorized for adults.Some parents on Friday expressed anguish over the news.“I’m feeling despair, despondent, frustrated, confused,” said Rachel Perera, a graduate student in Los Angeles and mother of an 8-month-old son. “I feel like the goal posts have been moving.”Ms. Perera said that she had been hoping to make a long-awaited trip to the East Coast this spring to see friends and introduce them to her son. She and her husband have been avoiding most contact with others during the Omicron wave in order to protect him.“I was hoping that we would have some hope, that it would help us get some semblance of normalcy,” she said of the vaccine for children under 5. “I feel like the world is moving on without us, the parents of little kids.”The F.D.A.’s most recent vaccine decisions have been highly fraught. Top Biden administration health officials pushed hard for authorization of booster shots in the fall, only to be forced to scale back their plans. But they were vindicated, some experts say, when the Omicron variant showed that it could more easily evade two-dose protection than its predecessor, the Delta variant.The Coronavirus Pandemic: Key Things to KnowCard 1 of 4Covid boosters.

The Food and Drug Administration asked to review Pfizer’s data on two doses now, while the company continues to assess whether three doses would be more effective.WASHINGTON — Pfizer and its partner, BioNTech, asked the Food and Drug Administration on Tuesday to authorize two doses of their coronavirus vaccine for children younger than 5 while the companies continue to research whether three doses would be more effective for the age group.In a highly unusual move, federal regulators pressed the companies to submit the request even though two doses failed to produce the hoped-for immune response among children 2 to 4 years old in a clinical trial. Only children between 6 months and 2 years old demonstrated an immune response comparable to that of older teenagers and young adults, the standard for a successful trial.The request for emergency authorization comes as the highly contagious Omicron variant has led to record numbers of infections. The under-5 group includes more than 19 million children, the only Americans not yet eligible for vaccination.The disappointing trial results, announced in December, prompted the companies to test a third low dose of the shot in that age group. But rather than wait until the end of March for the results, federal regulators decided to encourage Pfizer to apply for authorization of a two-dose regimen now in hopes of getting a head start on the vaccination effort.In meetings about the strategy, government officials argued that two doses had proved safe, even if they failed to produce an immune response in the whole age group, according to multiple people familiar with the discussions. Children in the trial received one-tenth of the adult dose.If children can get an initial injection this month, some officials reasoned, they will be ready for a third dose by the time researchers get what they hope will be successful results from the three-dose trial. The first two doses would be spaced three weeks apart, followed by a third dose two months after the second.Dr. Janet Woodcock, the acting F.D.A. commissioner, and Dr. Peter Marks, an agency regulator who oversees its vaccines office, said on Tuesday that it was important to act quickly given the surge in Omicron cases, which has now peaked in many parts of the country, and the likelihood that other variants would follow.An emergency meeting of the F.D.A.’s advisory group of outside experts is scheduled for Feb. 15, when they will discuss the request and make a recommendation. In an interview Tuesday, Dr. Paul A. Offit, a member of the group and director of the Vaccine Education Center at Children’s Hospital of Philadelphia, suggested that regulators could be short-circuiting the normal process without a clear rationale.“It doesn’t make sense we would approve a two-dose vaccine on the assumption the third dose would make up for deficiencies of the two doses,” he said.Albert Bourla, Pfizer’s chairman and chief executive, said in a statement that “ultimately, we believe that three doses of the vaccine will be needed for children 6 months through 4 years of age to achieve high levels of protection against current and potential future variants.” But he said that if two doses are authorized in the meantime, “parents will have the opportunity to begin a Covid-19 vaccination series for their children while awaiting potential authorization of a third dose.”Pfizer and BioNTech’s study of younger children was intended to measure immune responses, not the vaccine’s efficacy in preventing infections or severe cases of Covid-19. But because some children in the trial became infected, researchers got indications of how well the vaccine worked to stave off the virus, two people familiar with the study said. A similar development occurred in the companies’ study of their vaccine in 5- to 11-year-olds, which overlapped with a crushing wave of the Delta variant.One person familiar with the data, who spoke on condition of anonymity, said children 2 to 4 years old who were given two shots were infected at a rate 57 percent lower than the children in the placebo group. Children 6 months to 2 years old who got shots were infected at a rate 50 percent lower than the placebo group. There were fewer than 100 cases of symptomatic infection — a small fraction of the participants overall — and the margins of error were wide, that person said.The data also suggested that the vaccine better protected the children against infection from Delta than from Omicron. Omicron is better than Delta at evading the protection of both the Pfizer-BioNTech and Moderna vaccines in adults.The regulators’ strategy seemed based in part on the likelihood that the Pfizer-BioNTech’s three-dose trial would prove successful. Several experts, including Dr. Yvonne Maldonado, a Stanford professor of pediatric infectious diseases, said the history of vaccines suggested that a third dose would, in fact, enhance the immune response.“There’s almost no conceivable hypothesis where a third dose would be worse,” said Dr. Maldonado, a lead investigator at the Stanford site of Pfizer-BioNTech’s pediatric vaccine trials. “At worst it could be no different. So it might just be that two doses is the best you’re going to get.”Dr. H. Cody Meissner, another member of the F.D.A. advisory committee and chief of the pediatric infectious diseases division at Tufts Children’s Hospital, said he was open minded about the F.D.A.’s approach. But he said he worried about whether rare side effects might be missed in small-scale trials. The Pfizer-BioNTech trial included about 1,200 children younger than 2, and about 1,500 between 2 and 4, according to people familiar with the study’s design.The panel’s decision “will partly depend on what are the rates of hospitalization and severe disease in this age group,” Dr. Meissner said, “and what our sense is in terms of potential harm” should the two-dose regimen be authorized.The Coronavirus Pandemic: Key Things to KnowCard 1 of 4Omicron in retreat.

Pfizer and its partner BioNTech are expected as soon as Tuesday to ask the Food and Drug Administration to authorize a coronavirus vaccine for children under 5 years old as a two-dose regimen while they continue to research how well three doses work.Federal regulators are eager to review the data in hopes of authorizing shots for young children on an emergency basis as early as the end of February, according to multiple people familiar with the discussions, who were not authorized to speak publicly. If Pfizer waited for data on a three-dose regimen, the data would not be submitted until late March and the vaccine might not be authorized for that age group until late spring.Federal officials and Pfizer executives had been suggesting for days that an application for emergency authorization of a vaccine for children as young as 6 months was in the works. Every age group above that is eligible for shots, and the highly contagious Omicron variant has led to a sharp rise in infections among all ages, including children. There are more than 19 million Americans under 5 years old.Scott Gottlieb, a Pfizer board member and former commissioner of the Food and Drug Administration, told CBS News on Sunday that the vaccine might be authorized as soon as March for the youngest age group. The development was first reported by The Washington Post. Parents of younger children have been eager to see Pfizer and federal regulators move to make the shots available. Many families have said they are in limbo waiting out the Omicron wave and grappling with day care closures and child care crises.Federal officials are eager to begin a vaccination program for young children because the Pfizer-BioNTech studies showed two doses provided a notable level of protection against Covid-19 with no safety concerns, according to people who have been briefed on the data. Officials expect the regimen will eventually include three doses.Pfizer and BioNTech in mid-December announced that children 6 months to two years old who were given two doses of the vaccine at a tenth of the strength of adult doses produced an immune response comparable to that of young people ages 16 to 25. But among children ages 2 to 4, the response was less robust.The setback prompted the companies to test a third low dose of the shot in young children. Rather than wait for those results, federal regulators took the unusual approach of encouraging Pfizer to apply for authorization for a two-dose regimen to begin protecting children from the Omicron variant and other possible subsequent mutations, according to four people familiar with the strategy.Even though young children largely do well in combating the virus, the American Academy of Pediatrics says that the Omicron variant has intensified the threat of Covid-19 in children under 5.“Sadly, we are seeing the rates of hospitalizations increasing for children 0 to 4, children who are not yet currently eligible for Covid-19 vaccination,” Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, told reporters this month. She said the high rate of transmission of the Omicron variant was likely to blame.The Coronavirus Pandemic: Key Things to KnowCard 1 of 4Omicron in retreat.

The move clears the way for millions of teenagers to receive an additional shot, with a top regulator citing evidence that the effectiveness of two doses is waning in the age group.WASHINGTON — Federal regulators on Thursday authorized booster shots of the Pfizer-BioNTech coronavirus vaccine for another swath of the population, 16- and 17-year-olds, at least six months after they received their second shot of that vaccine. The move clears the way for several million teenagers to receive an additional shot.The decision by the Food and Drug Administration, which was expected, comes as initial laboratory tests have suggested that the new fast-spreading variant, Omicron, dulls the power of two doses of the Pfizer vaccine.Everyone 18 and older has been eligible since Nov. 19 to receive a booster six months after getting a second shot of the Pfizer or Moderna vaccine, or two months after a Johnson & Johnson shot. Nearly 50 million Americans — a quarter of those fully vaccinated — have gotten the additional shots.The F.D.A. broadened Pfizer’s authorization to cover the younger age group on an emergency basis. The Moderna and Johnson & Johnson vaccines remain authorized only for adults.“Since we first authorized the vaccine, new evidence indicates that vaccine effectiveness against Covid-19 is waning after the second dose of the vaccine for all adults and for those in the 16- and 17-year-old age group,” said Dr. Peter Marks, who oversees the F.D.A.’s vaccine division. A booster, he added, “will help provide continued protection against Covid-19 in this and older age groups.”Dr. Marks did not address whether vaccine effectiveness was also ebbing for 12- to 15-year-olds, who became eligible for the Pfizer vaccine in May.Regulators reviewed immune response data from adults that showed more robust antibody levels a month after booster doses were given. They said the analysis demonstrated the effectiveness of a booster shot for adolescents.Dr. Rochelle P. Walensky, the Centers for Disease Control and Prevention director, promptly signed off on the move, saying the agency was encouraging adolescents to receive a booster dose.“Although we don’t have all the answers on the Omicron variant, initial data suggests that Covid-19 boosters help broaden and strengthen the protection against Omicron and other variants,” she said in a statement.Before meeting his Covid-19 response team at the White House, President Biden called the development “even more great news from the F.D.A. and C.D.C.” He added, “I say it to all of you: If you got vaccinated six months ago, get your booster right away.”The F.D.A. and the C.D.C., which sets vaccine policy for the federal government, acted without input from their independent expert advisory panels. The committees have typically discussed whether to authorize or expand eligibility for shots in public meetings before the agencies act.Dr. Jesse L. Goodman, a former chief scientist at the F.D.A., said that given the spirited debate about boosters this fall among the agency’s regulators and outside advisers, more public discussion would have been helpful.“Transparency lets people make more informed decisions,” Dr. Goodman said. For instance, he said, recent data from Israel and elsewhere that suggests minimal serious side effects in younger, boosted people might help allay some parents’ concerns about a third dose for older male teenagers.Support for boosters has been growing among public health experts in the face of the Omicron variant; some who previously opposed them now support a broad campaign. The F.D.A.’s expert committee recommended rejecting Pfizer-BioNTech’s request in September to clear a booster shot for 16- and 17-year-olds, partly because of concerns over what the panel saw as insufficient data about a rare heart condition tied to the Pfizer-BioNTech and Moderna shots, especially in younger men.That condition, myocarditis, or inflammation of the heart muscle, can also be caused by the virus. Federal scientists have said that cases tend to be mild and resolve quickly.The Coronavirus Pandemic: Key Things to KnowCard 1 of 4The Omicron variant.