In the rush to understand the threat posed by the Omicron variant, the worrisome new version of the coronavirus, some experts are pointing hopefully to early signs that it may cause only mild illness, without some of the trademark symptoms of Covid.But it is far too early to assume that the variant will not cause severe illness, too, warned Dr. Richard Lessells, who coordinates clinical and epidemiological data for the South African Covid Variant Research Consortium.Many of the early infections in South Africa were spotted among younger people more likely to experience mild illness, he said. The picture may change as the virus spreads through the larger population. At the moment, the variant has been spotted in at least a dozen countries, including Britain and the Netherlands. Many others are closely monitoring cases. Omicron has not yet surfaced in the United States, according to the Centers for Disease Control and Prevention.Omicron has dozens of new mutations, including many that may enable the virus to be more contagious and to sidestep immune defenses. But Dr. Angelique Coetzee, who chairs the South African Medical Association, noted on Saturday that the nation’s hospitals were not overrun by patients infected with the new variant, and that most were not fully immunized.Moreover, most patients she had seen did not lose their sense of taste and smell, and had only a slight cough, she told reporters.But that may not be as reassuring as it sounds. Most of South Africa’s cases were initially found in the Gauteng province, mostly among younger people at universities and higher education institutions, said Dr. Lessells, who is also an infectious disease physician at the University of KwaZulu-Natal.“We would of course expect the vast majority of those to be mild cases anyway, regardless of vaccination status,” he said.In addition, cases overall have also been rising only in the last two weeks, Dr. Lessells noted: “There’s even barely enough time for infections to have had time to progress to severe disease and hospitalization.”Should Omicron cause severe illness, that will become apparent if there is a significant rise in hospitalizations over the next week or two, he added.Scientists have not yet analyzed infections in fully immunized people, but they are already seeing some cases of reinfection that suggest the variant can overcome natural immunity, Dr. Lessells said.He and his colleagues plan to review the latest data on Monday to spot trends and to plan for Omicron’s spread.

As infections rise, Americans over 18 will be permitted to get extra doses. But it’s not clear boosters really are needed by so many people, or that the shots will turn back the pandemic.Faced with rising infections and an anticipated surge in holiday travel, scientific advisers to the Centers for Disease Control and Prevention on Friday endorsed booster shots of the coronavirus vaccines for all Americans over 18.If formally adopted by the agency, the recommendation will fulfill President Biden’s pledge in August to make the extra doses available to all adults, capping months of scientific debate over whether most people really needed boosters. The shots are already available at many drugstores, doctors’ offices and vaccination centers.The C.D.C. advisers said that Americans over age 50, as well as those 18 and older living in long-term care facilities, “should” get booster shots of the Pfizer-BioNTech or Moderna vaccines. All other adults over age 18 “may” get booster doses, the panel decided. Recipients of Johnson & Johnson’s one-dose vaccine already were cleared to get a booster at least two months after the initial shot.Earlier on Friday, the Food and Drug Administration authorized booster shots for all Americans over age 18. But the C.D.C. usually sets the clinical guidelines adopted by the medical profession. The agency’s director, Dr. Rochelle Walensky, is expected to approve the panel’s recommendation later on Friday. Many experts worried that extra doses were not needed by most adults to prevent serious illness and death, and that a push for boosters could constrain global vaccine supplies even as people in many poor countries have not received their first doses.But infection rates are rising again in the United States and soaring in much of Europe. After recording more than 14,000 new infections on Thursday, Austria will go into a nationwide lockdown on Monday and impose a coronavirus vaccination mandate in February, the first such mandate in a Western democracy.Health officials in many of these countries, and now in the United States, see booster shots as a way of shoring up defenses against a tenacious enemy and gaining the upper hand in the pandemic. France, for example, has mandated booster shots for those over age 65 who wish to get a health pass permitting access to public venues.“Look what other countries are doing now about adopting a booster campaign virtually for everybody,” Dr. Anthony S. Fauci, the Biden administration’s top Covid adviser, said at a conference on Tuesday. “I think if we do that, and we do it in earnest, I think by the spring we can have pretty good control of this.”In the United States, infections have increased by 33 percent on average over the past two weeks, to 94,000 a day. The C.D.C.’s decision landed just as Americans prepare to spend the holidays with family and friends, gatherings likely to accelerate the trend.The shots may help forestall at least some infections, particularly in older adults and those with certain health conditions. But many experts, including some who advise federal agencies, are skeptical that boosters alone can turn the tide.The extra shots are unlikely to offer much benefit to adults under 65, who remain protected from severe illness and hospitalization by the initial immunization, the experts said. “Overall protection remains high for severe disease and hospitalization,” said Dr. Sara Oliver, an epidemiologist at the C.D.C., told the scientific advisers meeting on Friday. Moreover, more than 100 million Americans have not received even the first dose of a coronavirus vaccine. In the United States, as in Europe, deep pockets of vaccine-resistant adults are likely to prolong the pandemic, however well protected their neighbors may be.Many Americans seem unmoved by the sudden push for boosters. More than 85 percent of the adult population became eligible when the C.D.C. added depression and other mental illnesses to the list of conditions that qualify people for an extra vaccine dose. But only about 18 percent of those ages 18 and older have chosen to get one. And those may not be the people most in need of extra protection.Production of the Pfizer-BioNTech Covid vaccine in Puurs, Belgium.Pfizer, via Associated PressThe most effective strategy for the administration would be to rush booster doses to residents of nursing homes and long-term care facilities, said Dr. Celine Gounder, an infectious disease specialist at Bellevue Hospital Center. These are the adults mostly likely to benefit.At the moment, fully vaccinated white people are more likely to have obtained booster shots, compared with other racial and ethnic groups, according to data compiled by the Kaiser Family Foundation. At the scientific panel meeting, several experts noted that overly complicated eligibility criteria may be confusing many Americans and taxing health care providers. Americans who have opted for boosters “tend to be of higher socioeconomic status and more highly educated, and have more access in general to medical care,” Dr. Gounder said. “That’s not necessarily who’s actually at risk of severe disease, hospitalization or death, and so I think you’re going to have limited public health impact.”The Biden administration intends to provide booster shots in long-term care facilities and nursing homes, and work with community health centers to reach people with limited access to health care, said Ian Sams, a spokesman at the Department of Health and Human Services.There is reason to think more people may choose to get boosters in the coming weeks. While extra shots of the Pfizer-BioNTech vaccine have been available since late September, boosters of the Moderna and Johnson & Johnson vaccines were authorized roughly four weeks ago.And every week, more Americans will become eligible as they pass the six-month mark since their initial immunizations. At a vaccine clinic in Chelsea, Mass., people waited after receiving their shots earlier this month.Brian Snyder/ReutersAlthough federal officials have opted to double down on booster shots as the best hope for ending the pandemic, the scientific questions about their efficacy are far from settled.Dr. Fauci and other officials contend that protection from the vaccines is now waning over time, in all age groups, even against severe illness and hospitalization..css-1xzcza9{list-style-type:disc;padding-inline-start:1em;}.css-3btd0c{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:1rem;line-height:1.375rem;color:#333;margin-bottom:0.78125rem;}@media (min-width:740px){.css-3btd0c{font-size:1.0625rem;line-height:1.5rem;margin-bottom:0.9375rem;}}.css-3btd0c strong{font-weight:600;}.css-3btd0c em{font-style:italic;}.css-1kpebx{margin:0 auto;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-family:nyt-cheltenham,georgia,’times new roman’,times,serif;font-weight:700;font-size:1.375rem;line-height:1.625rem;}@media (min-width:740px){#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-1kpebx{font-size:1.25rem;line-height:1.4375rem;}}.css-1gtxqqv{margin-bottom:0;}.css-19zsuqr{display:block;margin-bottom:0.9375rem;}.css-12vbvwq{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;}@media (min-width:740px){.css-12vbvwq{padding:20px;width:100%;}}.css-12vbvwq:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-12vbvwq{border:none;padding:10px 0 0;border-top:2px solid #121212;}.css-12vbvwq[data-truncated] .css-rdoyk0{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-12vbvwq[data-truncated] .css-eb027h{max-height:300px;overflow:hidden;-webkit-transition:none;transition:none;}.css-12vbvwq[data-truncated] .css-5gimkt:after{content:’See more’;}.css-12vbvwq[data-truncated] .css-6mllg9{opacity:1;}.css-qjk116{margin:0 auto;overflow:hidden;}.css-qjk116 strong{font-weight:700;}.css-qjk116 em{font-style:italic;}.css-qjk116 a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;text-underline-offset:1px;-webkit-text-decoration-thickness:1px;text-decoration-thickness:1px;-webkit-text-decoration-color:#326891;text-decoration-color:#326891;}.css-qjk116 a:visited{color:#326891;-webkit-text-decoration-color:#326891;text-decoration-color:#326891;}.css-qjk116 a:hover{-webkit-text-decoration:none;text-decoration:none;}Israeli health officials are seeing a drop in immunity “not only against infection, but against hospitalizations, and to some extent death,” Dr. Fauci recently told “The Daily” podcast. The trend, he added, “is starting to now involve all age groups — it isn’t just the elderly.”But other experts disagree, pointing to studies showing that the vaccines remain highly effective against severe illness in adults under 65. The apparent waning of protection against infection may only result from vaccinated people taking fewer precautions, they say, and to the arrival of the more contagious Delta variant.Even if they did not provide much additional protection to most adults, booster shots still would be helpful if they helped curb transmission of the virus. Federal health officials have argued as much, citing dropping case numbers in Israel following its booster campaign.But in the United States, for reasons not fully understood, infections began falling in September, said Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia and an adviser to the F.D.A. “We were having a decrease here as well before we ever started booster doses,” he said.A booster shot should prevent people from becoming infected and limit their infectiousness to some extent. Still, some household studies indicate that vaccinated people are about half as likely as unvaccinated people to transmit the Delta variant, but the protective effect seems to decline over the following weeks. The administration’s time and effort would be better spent getting primary shots to the unvaccinated, said Virginia Pitzer, an epidemiologist at the Yale School of Public Health. “In most places,” she said, “unvaccinated people are still the ones who are driving a lot of the transmission.”A medical worker tended to a Covid patient at the Sheba Medical Center in Ramat Gan, Israel, in October.Nir Elias/ReutersMost experts agree that booster shots benefit adults over 65 and people with weak immune systems. But in the weeks since boosters were authorized, only 32 percent of older people have received extra vaccine doses.“I’m seeing a lot of people who would benefit from a third or booster dose who have not yet had their dose,” said Dr. Camille Kotton, an infectious disease physician at Massachusetts General Hospital and an adviser to the C.D.C.“Some of it is fatigue, some of it is not understanding the new guidance,” she added. “It’s very hard to understand for whom a booster dose is recommended at this point.”In Mississippi, Judy Spencer, 76, said she was in good health and did not plan to get a booster, as she had already received two doses of the Moderna vaccine. “I took the shot, I’m glad I did, but I’m through with it,” she said.Boosters and shots for children were administered at the Unidos En Salud community vaccination and testing site in San Francisco.Mike Kai Chen for The New York TimesThe picture for adults under 65 is muddled, and some experts balked at the prospect of extra shots because it was unclear whether the benefit would outweigh the potential risks. Men and boys under 30, in particular, are at slightly increased risk of developing rare and mild heart problems linked to the Pfizer-BioNTech and Moderna vaccines.Experts said the low rate of boosters to date could be at least partly blamed on the administration’s muddled messaging. In earlier recommendations, the C.D.C. specified groups of people who should get boosters because of their age, occupations or underlying medical risks.“C.D.C. speaks Latin,” Ned Lamont, the governor of Connecticut, said at a news conference on Thursday. “I can’t figure out who’s eligible, who’s not eligible.” Dr. Ashish Jha, dean of the Brown University School of Public Health, said, “It’s been very frustrating to watch the national conversation on boosters.”

After weeks of contradictory statements and confusing guidelines about which Americans need booster shots of coronavirus vaccines, federal health officials are poised to recommend them to everyone over 18.An advisory panel to the Centers for Disease Control and Prevention is scheduled to meet on Friday to weigh the pros and cons of recommending the boosters to all adults. But the discussion is not expected to turn up any surprises, and the final recommendations from the agency itself are likely to align with President Biden’s promise that all adults would be eligible for extra doses. The meeting is to begin at 12 p.m. Eastern time.Desperate to dampen even a dim echo of last winter’s horrors, the Biden administration is betting that booster shots will shore up what some have characterized as waning immunity among the fully vaccinated. The Food and Drug Administration authorized boosters of the Pfizer-BioNTech and Moderna vaccines for all adults on Friday.Research suggests that the shots may help forestall at least some infections, particularly in older adults and those with certain health conditions.After an all too brief respite, coronavirus infections are inching up again, particularly in parts of the country where cooler weather is hustling people indoors.The C.D.C.’s decision will land just as Americans are poised to travel, likely in record numbers, to spend the holidays with family and friends. Given the roughly 100 million Americans who have yet to receive a single dose of vaccine, holiday travel and get-togethers could send cases skyrocketing, as they did last year.Several European countries are also offering boosters to all adults in a bid to contain fresh waves of infections. France has gone so far as to mandate booster shots for those over age 65 who wish to get a health pass permitting access to public venues.“Look what other countries are doing now about adopting a booster campaign virtually for everybody,” Dr. Anthony S. Fauci, the Biden administration’s top Covid adviser, said at a conference on Tuesday. “I think if we do that, and we do it in earnest, I think by the spring we can have pretty good control of this.”But many experts, including some who advise federal agencies, are skeptical that boosters alone can turn the tide. While the extra shots can strengthen immunity in older adults, they are unlikely to offer much benefit to adults under 65, who remain protected from severe illness and hospitalization by the initial immunization, the experts said.It is also unclear whether booster shots can significantly slow the spread of the virus. The limited evidence available suggests that vaccines can blunt transmission, but only to a limited extent and for a limited period..css-1xzcza9{list-style-type:disc;padding-inline-start:1em;}.css-3btd0c{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:1rem;line-height:1.375rem;color:#333;margin-bottom:0.78125rem;}@media (min-width:740px){.css-3btd0c{font-size:1.0625rem;line-height:1.5rem;margin-bottom:0.9375rem;}}.css-3btd0c strong{font-weight:600;}.css-3btd0c em{font-style:italic;}.css-1kpebx{margin:0 auto;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-family:nyt-cheltenham,georgia,’times new roman’,times,serif;font-weight:700;font-size:1.375rem;line-height:1.625rem;}@media (min-width:740px){#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-1kpebx{font-size:1.25rem;line-height:1.4375rem;}}.css-1gtxqqv{margin-bottom:0;}.css-19zsuqr{display:block;margin-bottom:0.9375rem;}.css-12vbvwq{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;}@media (min-width:740px){.css-12vbvwq{padding:20px;width:100%;}}.css-12vbvwq:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-12vbvwq{border:none;padding:10px 0 0;border-top:2px solid #121212;}.css-12vbvwq[data-truncated] .css-rdoyk0{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-12vbvwq[data-truncated] .css-eb027h{max-height:300px;overflow:hidden;-webkit-transition:none;transition:none;}.css-12vbvwq[data-truncated] .css-5gimkt:after{content:’See more’;}.css-12vbvwq[data-truncated] .css-6mllg9{opacity:1;}.css-qjk116{margin:0 auto;overflow:hidden;}.css-qjk116 strong{font-weight:700;}.css-qjk116 em{font-style:italic;}.css-qjk116 a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;text-underline-offset:1px;-webkit-text-decoration-thickness:1px;text-decoration-thickness:1px;-webkit-text-decoration-color:#326891;text-decoration-color:#326891;}.css-qjk116 a:visited{color:#326891;-webkit-text-decoration-color:#326891;text-decoration-color:#326891;}.css-qjk116 a:hover{-webkit-text-decoration:none;text-decoration:none;}Many pandemic-weary Americans, too, seem unmoved by the administration’s push for boosters. More than 85 percent of the adult population is already eligible, but only about 17 percent has chosen to get them. And those may not be the people most in need of extra protection.As with the initial shots, fully vaccinated white people are more likely to have lined up for a booster shot, compared with other racial and ethnic groups, according to data compiled by the Kaiser Family Foundation.So far, the people who have opted for boosters “tend to be of higher socioeconomic status and more highly educated, and have more access in general to medical care,” said Dr. Celine Gounder, an infectious disease specialist at Bellevue Hospital Center.“That’s not necessarily who’s actually at risk of severe disease, hospitalization or death, and so I think you’re going to have limited public health impact.”

Scientific advisers to the Centers for Disease Control and Prevention on Tuesday unanimously endorsed the Pfizer-BioNTech coronavirus vaccine for children ages 5 through 11, a move that will buttress defenses against a possible surge as winter arrives and ease the worries of tens of millions of pandemic-weary parents.If Dr. Rochelle Walensky, the agency’s director, formally accepts the recommendation, as expected, inoculations for these children could begin as soon as this week. Dr. Walensky made a brief appearance as the meeting began, noting that the day was “one that many of us have been very eager to see.”The C.D.C. panel’s endorsement arrives just as Americans prepare for a potentially risky holiday season. Cases in the United States have been falling steadily for weeks, but experts have warned that indoor gatherings may send the rates soaring again. Many Americans seem determined to celebrate; already airlines are bracing for what may be the busiest travel season since the start of the pandemic.While relatively few of the 29 million children in this age group will be fully immunized a month from now, even partial vaccination will provide some protection against the coronavirus. Every million doses given to children ages 5 to 11 would prevent about 58,000 cases and 226 hospitalizations in that group, according to the C.D.C.Immunizing these children is expected to prevent about 600,000 new cases from November 2021 to March 2022. And rising immunity may reduce the chances that young children will transmit the virus to vulnerable adults in their families and communities, health officials noted.Vaccinations of younger children are likely to help keep schools open. Virus outbreaks forced about 2,300 schools to close between early August and October, affecting more than 1.2 million students, according to data presented at the committee meeting.The pandemic has also stalled routine immunizations, widened education gaps and escalated rates of anxiety and depression among children. “Vaccination of children ages 5 to 11 years will not only help prevent Covid-19 infection and serious consequences of infection in this age group, but will also help children emotionally and socially,” said Dr. Pamela Rockwell, who represents the American Academy of Family Physicians on the C.D.C. panel.Still, about three in 10 parents say they will definitely not get the vaccine for their 5- to 11-year-old child, according to the most recent poll by the Kaiser Family Foundation. Only about three in 10 parents said they would immunize their child “right away,” a percentage that has barely budged since similar polls in July and September.Many other parents are eager to see their children vaccinated as quickly as possible. Anticipating the C.D.C.’s decision, the Biden administration has enlisted more than 20,000 pediatricians, family doctors and pharmacies to administer the shots. About 15 million doses are already being shipped to vaccination sites across the country, federal officials said on Monday.Daniel E. Slotnik contributed reporting.

Is the Pfizer-BioNTech vaccine safe for children ages 5 to 11? Does it work? Does every child need it?The Food and Drug Administration on Friday authorized the vaccine for emergency use in those age groups, following a near-unanimous recommendation from its advisers last week. On Tuesday, a similar committee advising the Centers for Disease Control and Prevention will have its say.If, as expected, the advisers recommend the vaccine and the agency’s director, Dr. Rochelle Walensky, signs off, the decision would most likely ease the worries of millions of parents and buttress the United States’ defenses against the virus before winter arrives.Inoculations for children ages 5 through 11 could then begin this week. Anticipating the agency’s decision, the Biden administration has enlisted more than 20,000 pediatricians, family doctors and pharmacies to administer the vaccines.About 15 million doses are already being packed with dry ice, loaded into small specialized containers and shipped via airplanes and trucks to vaccination sites across the country, federal officials said on Monday.The younger children will receive one-third of the dose authorized for those 12 and older, delivered by smaller needles and stored in smaller vials to avoid a mix-up with adult doses.The C.D.C.’s guidelines for the vaccine’s use are not legally binding, but heavily influence the medical community’s practice. An endorsement would be timely, as Americans begin to plan for the winter holidays.Although cases in the United States have been falling steadily for weeks, experts warn that indoor family gatherings during the Thanksgiving and Christmas holidays may send the rates soaring again, even if not to the horrific highs of last year. Airlines are preparing for what may be the busiest travel season since the start of the pandemic.Vaccinations would ease the minds of many parents who are anxious to protect their young children and frustrated by frequent school shutdowns and quarantines. Outbreaks of the coronavirus forced 2,000 schools to close between early August and October.Still, many parents are hesitant to immunize their children, citing concerns about long-term safety of the vaccine or because they fear that the vaccine is more harmful than Covid-19..css-1kpebx{margin:0 auto;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-family:nyt-cheltenham,georgia,’times new roman’,times,serif;font-weight:700;font-size:1.375rem;line-height:1.625rem;}@media (min-width:740px){#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-1kpebx{font-size:1.25rem;line-height:1.4375rem;}}.css-1gtxqqv{margin-bottom:0;}.css-k59gj9{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;width:100%;}.css-1e2usoh{font-family:inherit;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-box-pack:justify;-webkit-justify-content:space-between;-ms-flex-pack:justify;justify-content:space-between;border-top:1px solid #ccc;padding:10px 0px 10px 0px;background-color:#fff;}.css-1jz6h6z{font-family:inherit;font-weight:bold;font-size:1rem;line-height:1.5rem;text-align:left;}.css-1t412wb{box-sizing:border-box;margin:8px 15px 0px 15px;cursor:pointer;}.css-hhzar2{-webkit-transition:-webkit-transform ease 0.5s;-webkit-transition:transform ease 0.5s;transition:transform ease 0.5s;}.css-t54hv4{-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-1r2j9qz{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-e1ipqs{font-size:1rem;line-height:1.5rem;padding:0px 30px 0px 0px;}.css-e1ipqs a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;}.css-e1ipqs a:hover{-webkit-text-decoration:none;text-decoration:none;}.css-1o76pdf{visibility:show;height:100%;padding-bottom:20px;}.css-1sw9s96{visibility:hidden;height:0px;}.css-1in8jot{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;font-family:’nyt-franklin’,arial,helvetica,sans-serif;text-align:left;}@media (min-width:740px){.css-1in8jot{padding:20px;width:100%;}}.css-1in8jot:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1in8jot{border:none;padding:10px 0 0;border-top:2px solid #121212;}What to Know About Covid-19 Booster ShotsThe F.D.A. has authorized booster shots for millions of recipients of the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines. Pfizer and Moderna recipients who are eligible for a booster include people 65 and older, and younger adults at high risk of severe Covid-19 because of medical conditions or where they work. Eligible Pfizer and Moderna recipients can get a booster at least six months after their second dose. All Johnson & Johnson recipients will be eligible for a second shot at least two months after the first.Yes. The F.D.A. has updated its authorizations to allow medical providers to boost people with a different vaccine than the one they initially received, a strategy known as “mix and match.” Whether you received Moderna, Johnson & Johnson or Pfizer-BioNTech, you may receive a booster of any other vaccine. Regulators have not recommended any one vaccine over another as a booster. They have also remained silent on whether it is preferable to stick with the same vaccine when possible.The C.D.C. has said the conditions that qualify a person for a booster shot include: hypertension and heart disease; diabetes or obesity; cancer or blood disorders; weakened immune system; chronic lung, kidney or liver disease; dementia and certain disabilities. Pregnant women and current and former smokers are also eligible.The F.D.A. authorized boosters for workers whose jobs put them at high risk of exposure to potentially infectious people. The C.D.C. says that group includes: emergency medical workers; education workers; food and agriculture workers; manufacturing workers; corrections workers; U.S. Postal Service workers; public transit workers; grocery store workers.Yes. The C.D.C. says the Covid vaccine may be administered without regard to the timing of other vaccines, and many pharmacy sites are allowing people to schedule a flu shot at the same time as a booster dose.About three in 10 parents say they will definitely not get the vaccine for their 5- to 11-year-old children, according to the most recent poll by the Kaiser Family Foundation. A similar percentage of parents said that they would immunize their children “right away,” a figure that has barely budged since similar polls in July and September.Before the F.D.A. advisers met last week, they were bombarded by thousands of emails spouting misinformation about the vaccine and asking the experts to vote against it. One common objection to the vaccine holds that children rarely get sick from the virus, and the vaccine’s potential harms may outweigh its benefits.But while children are much less likely than adults to become seriously ill from the virus, their risk is not zero. Many children were infected with the coronavirus in the most recent surge, and children ages 5 through 11 accounted for nearly 11 percent of all cases the week of Oct. 10, according to data collected by the C.D.C.Since the beginning of the pandemic, more than 8,300 children ages 5 to 11 have been hospitalized with Covid, and at least 94 have died. About one-third of the hospitalized children were sick enough to be admitted to intensive care units.

Is the Pfizer-BioNTech vaccine safe for children ages 5 to 11? Does it work? Does every child need it?The Food and Drug Administration on Friday authorized the vaccine for emergency use in those age groups, following a near-unanimous recommendation from its advisers last week. On Tuesday, a similar committee advising the Centers for Disease Control and Prevention will have its say.If, as expected, the advisers recommend the vaccine and the agency’s director, Dr. Rochelle Walensky, signs off, the decision would most likely ease the worries of millions of parents and buttress the United States’ defenses against the virus before winter arrives.Inoculations for children ages 5 through 11 could then begin this week. Anticipating the agency’s decision, the Biden administration has enlisted more than 20,000 pediatricians, family doctors and pharmacies to administer the vaccines.About 15 million doses are already being packed with dry ice, loaded into small specialized containers and shipped via airplanes and trucks to vaccination sites across the country, federal officials said on Monday.The younger children will receive one-third of the dose authorized for those 12 and older, delivered by smaller needles and stored in smaller vials to avoid a mix-up with adult doses.The C.D.C.’s guidelines for the vaccine’s use are not legally binding, but heavily influence the medical community’s practice. An endorsement would be timely, as Americans begin to plan for the winter holidays.Although cases in the United States have been falling steadily for weeks, experts warn that indoor family gatherings during the Thanksgiving and Christmas holidays may send the rates soaring again, even if not to the horrific highs of last year. Airlines are preparing for what may be the busiest travel season since the start of the pandemic.Vaccinations would ease the minds of many parents who are anxious to protect their young children and frustrated by frequent school shutdowns and quarantines. Outbreaks of the coronavirus forced 2,000 schools to close between early August and October.Still, many parents are hesitant to immunize their children, citing concerns about long-term safety of the vaccine or because they fear that the vaccine is more harmful than Covid-19..css-1kpebx{margin:0 auto;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-family:nyt-cheltenham,georgia,’times new roman’,times,serif;font-weight:700;font-size:1.375rem;line-height:1.625rem;}@media (min-width:740px){#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-1kpebx{font-size:1.25rem;line-height:1.4375rem;}}.css-1gtxqqv{margin-bottom:0;}.css-k59gj9{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;width:100%;}.css-1e2usoh{font-family:inherit;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-box-pack:justify;-webkit-justify-content:space-between;-ms-flex-pack:justify;justify-content:space-between;border-top:1px solid #ccc;padding:10px 0px 10px 0px;background-color:#fff;}.css-1jz6h6z{font-family:inherit;font-weight:bold;font-size:1rem;line-height:1.5rem;text-align:left;}.css-1t412wb{box-sizing:border-box;margin:8px 15px 0px 15px;cursor:pointer;}.css-hhzar2{-webkit-transition:-webkit-transform ease 0.5s;-webkit-transition:transform ease 0.5s;transition:transform ease 0.5s;}.css-t54hv4{-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-1r2j9qz{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-e1ipqs{font-size:1rem;line-height:1.5rem;padding:0px 30px 0px 0px;}.css-e1ipqs a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;}.css-e1ipqs a:hover{-webkit-text-decoration:none;text-decoration:none;}.css-1o76pdf{visibility:show;height:100%;padding-bottom:20px;}.css-1sw9s96{visibility:hidden;height:0px;}.css-1in8jot{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;font-family:’nyt-franklin’,arial,helvetica,sans-serif;text-align:left;}@media (min-width:740px){.css-1in8jot{padding:20px;width:100%;}}.css-1in8jot:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1in8jot{border:none;padding:10px 0 0;border-top:2px solid #121212;}What to Know About Covid-19 Booster ShotsThe F.D.A. has authorized booster shots for millions of recipients of the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines. Pfizer and Moderna recipients who are eligible for a booster include people 65 and older, and younger adults at high risk of severe Covid-19 because of medical conditions or where they work. Eligible Pfizer and Moderna recipients can get a booster at least six months after their second dose. All Johnson & Johnson recipients will be eligible for a second shot at least two months after the first.Yes. The F.D.A. has updated its authorizations to allow medical providers to boost people with a different vaccine than the one they initially received, a strategy known as “mix and match.” Whether you received Moderna, Johnson & Johnson or Pfizer-BioNTech, you may receive a booster of any other vaccine. Regulators have not recommended any one vaccine over another as a booster. They have also remained silent on whether it is preferable to stick with the same vaccine when possible.The C.D.C. has said the conditions that qualify a person for a booster shot include: hypertension and heart disease; diabetes or obesity; cancer or blood disorders; weakened immune system; chronic lung, kidney or liver disease; dementia and certain disabilities. Pregnant women and current and former smokers are also eligible.The F.D.A. authorized boosters for workers whose jobs put them at high risk of exposure to potentially infectious people. The C.D.C. says that group includes: emergency medical workers; education workers; food and agriculture workers; manufacturing workers; corrections workers; U.S. Postal Service workers; public transit workers; grocery store workers.Yes. The C.D.C. says the Covid vaccine may be administered without regard to the timing of other vaccines, and many pharmacy sites are allowing people to schedule a flu shot at the same time as a booster dose.About three in 10 parents say they will definitely not get the vaccine for their 5- to 11-year-old children, according to the most recent poll by the Kaiser Family Foundation. A similar percentage of parents said that they would immunize their children “right away,” a figure that has barely budged since similar polls in July and September.Before the F.D.A. advisers met last week, they were bombarded by thousands of emails spouting misinformation about the vaccine and asking the experts to vote against it. One common objection to the vaccine holds that children rarely get sick from the virus, and the vaccine’s potential harms may outweigh its benefits.But while children are much less likely than adults to become seriously ill from the virus, their risk is not zero. Many children were infected with the coronavirus in the most recent surge, and children ages 5 through 11 accounted for nearly 11 percent of all cases the week of Oct. 10, according to data collected by the C.D.C.Since the beginning of the pandemic, more than 8,300 children ages 5 to 11 have been hospitalized with Covid, and at least 94 have died. About one-third of the hospitalized children were sick enough to be admitted to intensive care units.

The latest data is reassuring. Myocarditis remains very uncommon, and it is almost always mild and temporary. The heart risk from Covid-19 itself is far greater.Federal regulators are reviewing data on the link between Moderna’s coronavirus vaccine and a rare heart problem in adolescents, the company announced on Sunday. That side effect — myocarditis, an inflammation of the heart muscle — has also worried advisers to federal agencies in deliberations regarding use of the Pfizer-BioNTech vaccine in younger children and teenagers.Scientists advising the Centers for Disease Control and Prevention will review the latest data on the condition at a meeting on Tuesday before deciding whether to recommend the Pfizer-BioNTech vaccine for younger children.So how common is myocarditis, really? And should parents be concerned about vaccinating their children?Absolutely not, said several experts familiar with the recent studies. While the vaccines made by Pfizer-BioNTech and Moderna do seem to be associated with an increased risk of myocarditis, the absolute risk remains very small. Most cases are mild and resolve quickly.“If you look at an isolated risk, you could really get yourself very worked up and scared,” said Dr. Brian Feingold, an expert on heart inflammation in children at UPMC Children’s Hospital of Pittsburgh.But Covid-19 itself, he noted, is much more apt to damage the heart permanently: “Statistically, that’s way more likely.”Myocarditis generally results from infection with a virus or bacteria, and causes symptoms like rapid or irregular heartbeat, chest pain and shortness of breath. Globally, about 10 to 20 people out of every 100,000 develop myocarditis each year, but many others have mild symptoms and may never be diagnosed.Since the start of the coronavirus pandemic, tens of thousands of children have been hospitalized with Covid, and 657 have died, according to data collected by the C.D.C.Some children who are infected with the coronavirus may go on to develop long Covid, remaining ill for months after the initial infection is gone, or multisystem inflammatory syndrome, which has affected at least 5,200 children in the United States.While the risk of myocarditis after vaccination is real, “those are real numbers that are bigger,” Dr. Feingold said.The incidence of myocarditis after vaccination varies with age, sex and dose — and across studies. But the trend so far suggests that the chances are highest after the second dose of an mRNA vaccine in male patients age 16 to 29.There are roughly 11 cases of myocarditis for every 100,000 vaccinated male patients in this age group, one study estimated. The odds of myocarditis decrease with age.Data on adolescents age 12 to 15 years is limited, because the Pfizer-BioNTech vaccine only recently became available to them. But so far, heart problems after vaccination seem to be less common in boys of that age than in older men, said Dr. Paul A. Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia.This age distribution is similar to that seen among patients with myocarditis caused by viral infections, Dr. Offit said.An F.D.A. scientific advisory committee, on which he sits, met last week to review the Pfizer-BioNTech vaccine’s safety in children 5 through 11 and ultimately voted to recommend that children be given the vaccine.“Myocarditis is usually a post-pubertal phenomenon,” Dr. Offit said, adding, “That made me feel better about the fact that we won’t be unpleasantly surprised” by a surge in myocarditis in younger children after they are immunized.It’s unclear why myocarditis seems to affect boys more often than girls, and whether it is specific to the coronavirus vaccines or a side effect of all mRNA vaccines.Matt Slocum/Associated PressThat reassurance may not be enough for some parents. Jeff Gustin, a plant geneticist at the Agriculture Department, said he and two of his sons had elevated heart rates after getting the Pfizer-BioNTech vaccine.His teenage sons recovered quickly, but Dr. Gustin, 42, says he can still feel his heart beating hard, especially when he lies down. Now he is considering a booster of the Johnson & Johnson vaccine, rather than of the Pfizer-BioNTech or Moderna vaccine.And given the family history, he is hesitant to have his youngest son, who is 11, immunized unless the school district requires it.But some instances of myocarditis after immunization, like those of Dr. Gustin’s older sons, may be detected simply because of the intense scrutiny on vaccines, said Dr. James de Lemos, a cardiologist at the University of Texas Southwestern Medical Center in Dallas, who reported one of the first cases in January..css-1kpebx{margin:0 auto;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-family:nyt-cheltenham,georgia,’times new roman’,times,serif;font-weight:700;font-size:1.375rem;line-height:1.625rem;}@media (min-width:740px){#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-1kpebx{font-size:1.25rem;line-height:1.4375rem;}}.css-1gtxqqv{margin-bottom:0;}.css-k59gj9{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;width:100%;}.css-1e2usoh{font-family:inherit;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-box-pack:justify;-webkit-justify-content:space-between;-ms-flex-pack:justify;justify-content:space-between;border-top:1px solid #ccc;padding:10px 0px 10px 0px;background-color:#fff;}.css-1jz6h6z{font-family:inherit;font-weight:bold;font-size:1rem;line-height:1.5rem;text-align:left;}.css-1t412wb{box-sizing:border-box;margin:8px 15px 0px 15px;cursor:pointer;}.css-hhzar2{-webkit-transition:-webkit-transform ease 0.5s;-webkit-transition:transform ease 0.5s;transition:transform ease 0.5s;}.css-t54hv4{-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-1r2j9qz{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-e1ipqs{font-size:1rem;line-height:1.5rem;padding:0px 30px 0px 0px;}.css-e1ipqs a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;}.css-e1ipqs a:hover{-webkit-text-decoration:none;text-decoration:none;}.css-1o76pdf{visibility:show;height:100%;padding-bottom:20px;}.css-1sw9s96{visibility:hidden;height:0px;}.css-1in8jot{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;font-family:’nyt-franklin’,arial,helvetica,sans-serif;text-align:left;}@media (min-width:740px){.css-1in8jot{padding:20px;width:100%;}}.css-1in8jot:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1in8jot{border:none;padding:10px 0 0;border-top:2px solid #121212;}What to Know About Covid-19 Booster ShotsThe F.D.A. has authorized booster shots for millions of recipients of the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines. Pfizer and Moderna recipients who are eligible for a booster include people 65 and older, and younger adults at high risk of severe Covid-19 because of medical conditions or where they work. Eligible Pfizer and Moderna recipients can get a booster at least six months after their second dose. All Johnson & Johnson recipients will be eligible for a second shot at least two months after the first.Yes. The F.D.A. has updated its authorizations to allow medical providers to boost people with a different vaccine than the one they initially received, a strategy known as “mix and match.” Whether you received Moderna, Johnson & Johnson or Pfizer-BioNTech, you may receive a booster of any other vaccine. Regulators have not recommended any one vaccine over another as a booster. They have also remained silent on whether it is preferable to stick with the same vaccine when possible.The C.D.C. has said the conditions that qualify a person for a booster shot include: hypertension and heart disease; diabetes or obesity; cancer or blood disorders; weakened immune system; chronic lung, kidney or liver disease; dementia and certain disabilities. Pregnant women and current and former smokers are also eligible.The F.D.A. authorized boosters for workers whose jobs put them at high risk of exposure to potentially infectious people. The C.D.C. says that group includes: emergency medical workers; education workers; food and agriculture workers; manufacturing workers; corrections workers; U.S. Postal Service workers; public transit workers; grocery store workers.Yes. The C.D.C. says the Covid vaccine may be administered without regard to the timing of other vaccines, and many pharmacy sites are allowing people to schedule a flu shot at the same time as a booster dose.The myocarditis linked to the vaccines is far less frequent and severe compared with that observed in patients with Covid, and it does not seem to cause lasting harm, Dr. de Lemos said.The coronavirus can infect cardiac muscle, as well as the lining of blood vessels, putting the heart and other organs at risk of long-term damage. The virus can also weaken the heart enough to require a transplant, and even cause lethal damage.By contrast, the myocarditis observed after vaccination is mild and transient. “It’s unsettling, but rarely life-threatening,” Dr. de Lemos said.Still, some Northern European countries, where the Moderna vaccine was already approved for adolescents, have stopped giving it to people age 30 and younger, at least for the moment. That decision was based on evidence suggesting that the risk of myocarditis is higher with the Moderna vaccine than with the Pfizer-BioNTech vaccine.When researchers at Kaiser Permanente Northern California directly compared the two vaccines, for example, they found that in men 18 to 39 the incidence of myocarditis was elevated after a dose of either vaccine, but more so after Moderna’s.“The rate after Moderna is objectively higher than the rate after Pfizer,” said Dr. Nicola P. Klein, director of the Kaiser Permanente Vaccine Study Center. “It’s consistent, regardless of which cases we use, or whether it’s males only or both sexes.”The risk after both doses of the Moderna vaccine in people age 18 to 39 was as much as 37 times as high as in the general population, and the rate after two doses of the Pfizer-BioNTech vaccine in those age 12 to 39 was as much as 19 times as high.While that may sound alarming, the absolute numbers were still tiny, Dr. de Lemos noted. “Thirty times a small number is still a small number,” he said. “The math still favors vaccination in adolescents and children.”It’s unclear why myocarditis seems to affect boys more often than girls, and whether it is specific to the coronavirus vaccines or a side effect of all mRNA vaccines. The focus on myocarditis after vaccination may also help to understand the condition generally, experts said.“I’ll feel a lot better about this when we have an understanding of the pathogenesis, of exactly what is it that’s going on,” Dr. Offit said. If doctors can identify the cause, he added, “we may be able to treat it to some extent.”

Pregnant and breastfeeding women respond to the first dose of the coronavirus vaccines more slowly than other women, and mount a less potent defense against the virus, according to a new study. After the second dose, however, their response looks almost normal. The results, published this month in the journal Science Translational Medicine, suggest that pregnant and breastfeeding women remain susceptible to the virus for longer after vaccination. The study underscores the importance of giving these women the second dose in time, and monitoring them closely in the meantime for signs of infection.During pregnancy, the immune system is modified to tolerate the fetus — effectively a foreign entity — leaving pregnant women particularly susceptible to pathogens like the coronavirus. Because of this, pregnant women are more likely to become severely ill and to die from Covid than other women of the same age.Earlier research had suggested that pregnancy might also dampen the response to vaccines. But the initial trials of Covid vaccines did not include pregnant and breastfeeding women because of safety concerns, so there has been limited information about how well they respond to the inoculations.The researchers analyzed the antibodies produced by 84 pregnant women, 31 breastfeeding women and 16 nonpregnant women of the same ages, immunized with the coronavirus vaccines made by Pfizer-BioNTech or Moderna.After the first dose, pregnant and breastfeeding women had fewer antibodies than other women of the same age. And the antibodies were less effective at recruiting other parts of the immune system to fight the virus.Two to six weeks after the second dose, pregnant and breastfeeding women had about as many antibodies as other women their age, consistent with results from other studies, and the qualitative differences also narrowed.Breastfeeding women boosted their response more effectively than pregnant women after the second dose, and the quality of their immune response more closely resembled that of nonpregnant women.The women in the study were immunized at different times during pregnancy. Future studies should analyze the optimal time during pregnancy to deliver the vaccines, the researchers said.

The coronavirus vaccine made by Moderna is safe and produces a powerful immune response in children 6 through 11, the company said on Monday.One month after immunization was complete, the children in Moderna’s trial had antibody levels that were 1.5 times higher than those seen in young adults, the company said.Moderna did not release the full data, nor are the results published in a peer-reviewed journal. The results were announced one day before an advisory committee of the Food and Drug Administration is scheduled to review data for the Pfizer-BioNTech vaccine in children 5 through 11.Moderna tested two shots of the vaccine given 28 days apart in 4,753 children. They received 50 micrograms of vaccine, half the adult dose, in each shot. (Last week, based on data showing that the half dose is still highly effective, the F.D.A. authorized a booster shot of the Moderna vaccine at this dose.)Moderna submitted study results for the vaccine’s use for adolescents 12 through 17 in June, but the F.D.A. has not yet announced a decision for that age group. Some research indicates that the Moderna vaccine may increase the risk of a rare side effect called myocarditis, an inflammation of the heart muscle, in boys and young men. In July, the F.D.A. asked both Pfizer and Moderna to expand the size of their trials in order to detect less common side effects.In children aged 6 through 11, most of the side events were mild or moderate; the most common were fatigue, headache, fever and pain at the injection site, Moderna said in its statement on Monday. An independent committee will continue to review the vaccine’s safety in the trial participants for 12 months after the second dose.Moderna is still recruiting children aged 2 through 5 and 6 months to under 2 years for trials of the vaccine in those age groups. The company has enrolled about 5,700 children in the United States and Canada in the trial.Moderna plans to submit the results soon to the F.D.A. and to regulatory agencies in Europe and elsewhere, the company said.

“In our hearts, I think people don’t quite agree with this notion of a booster dose,” said one leading vaccine expert.Following a series of endorsements over the last month by scientific panels advising federal agencies, tens of millions of Americans are now eligible for booster shots of coronavirus vaccines.But the recommendations — even those approved unanimously — mask significant dissent and disquiet among those advisers about the need for booster shots in the United States.In interviews last week, several advisers to the Centers for Disease Control and Prevention and to the Food and Drug Administration said data show that, with the exception of adults over age 65, the vast majority of Americans are already well protected against severe illness and do not need booster shots.All the advisers felt that they were obligated to make difficult choices, based on sparse research, in the middle of a public health emergency. But some said they felt compelled to vote for the shots because of the way the federal agencies framed the questions that they were asked to consider.Other committee experts said that they wanted to avoid confusing the public further by dissenting, or that they voted according to their views of the evidence and were simply overruled.“These are not evidence-based recommendations,” said Dr. Sarah S. Long, a pediatric infectious disease expert at Drexel University College of Medicine in Philadelphia, and a member of the C.D.C.’s Advisory Committee on Immunization Practices.Following a series of votes, the official position of the F.D.A. and C.D.C. now is that older adults, people with certain medical conditions and those whose jobs or living situations regularly expose them to the virus can opt for a booster dose of any of the three vaccines.The C.D.C. also advised last week that people in certain high-risk groups who got one type of Covid-19 vaccine could choose a different one for their booster.“I don’t think that we have evidence that everybody in those groups needs a booster today,” said Dr. Matthew Daley, senior investigator at Kaiser Permanente Colorado and a member of the C.D.C. advisory committee.Dr. Long and Dr. Daley both voted in favor of booster shots at their committee’s meeting on Thursday, but with reservations over how the decision would be viewed by anxious Americans who might conclude mistakenly that the vaccines are ineffective.When the C.D.C. committee reviewed evidence for the Pfizer-BioNTech booster in September, the advisers agreed unanimously only on extra shots for adults over age 65. Two of the 15 panelists voted against booster doses for adults over age 50 with certain medical conditions.Approval of boosters for people aged 18 to 49 with other medical risk factors squeaked by in a vote of nine to six. And the booster recommendation for people whose occupations put them at risk did not pass.That last category was included in the final C.D.C. recommendations only because Dr. Rochelle Walensky, the agency’s director, overruled her advisers.“You can see the hesitancy in all this,” said Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia and a member of the F.D.A.’s vaccine advisory committee. “It’s because in our hearts, I think people don’t quite agree with this notion of a booster dose.”“The door just got bigger and bigger and bigger, it got wider and wider with each step,” Dr. Offit added. “The companies got what they wanted, the administration got what they wanted.”Dr. Rochelle Walensky, the C.D.C. director, overruled agency advisers and broadened the number of Americans eligible for booster shots.Pool photo by Jim Lo ScalzoIn interviews, the experts bemoaned the limited data on the safety and efficacy of the booster shots. The data supporting extra doses of the Moderna and Johnson & Johnson vaccines was “of very low quality,” Dr. Kathleen Dooling, a C.D.C. scientist, acknowledged at the committee meeting on Thursday.Still, some said they felt they had to vote in favor of booster shots of the Moderna and Johnson & Johnson vaccines because they had already recommended boosters of the Pfizer-BioNTech vaccine and did not want to deny other Americans.“The problem that troubled me is that we don’t know if boosters are necessary,” said Dr. Cody Meissner, a professor of pediatrics at Tufts University School of Medicine and a member of the F.D.A. advisory committee.But “if you’re going do it for one group, I think fairness kind of dictates you have to do it for all the groups,” he added.In interviews, panelists were hesitant to voice their discomfort, saying they did not want to undercut the final decisions from the committees.“It’s hard to show some of the misgivings, because we don’t want to have mixed messaging,” said Dr. Camille Kotton, an infectious disease physician at Massachusetts General Hospital and a member of the C.D.C. committee.But several panelists who did not wish to speak on the record said privately that the final recommendations for booster shots were inevitable as soon as President Biden promised them to all adults.“We are in a very difficult position to do much of anything other than what everybody has already announced that we’ve done,” said Dr. Long, one of the few to publicly express her unhappiness.Some administration officials “pay lip service to science and the evidence,” she said.Experts outside these committees also said that President Biden’s promise of boosters, in August, made it difficult for the agencies to weigh the data objectively in September and October.“The perception is that the horse is out of the barn, and there’s not really much you can do at this point,” said Dr. Celine Gounder, an infectious disease specialist at Bellevue Hospital Center who has previously advised the Biden administration.“The fact is, you can’t have this confusing mess — it’s going to create more problems,” she added, referring to mixed signals from the White House and federal scientists.Much of the dissent in recent hearings sprang from one central contention: that the coronavirus vaccines, like nearly all other vaccines, should be used to prevent illness severe enough to require medical attention, not milder infection.The bulk of the evidence presented to the federal advisers demonstrated only that the original immunizations were waning in potency against infections. The vaccines seem to be holding steady against severe Covid-19 and death, except perhaps in older Americans..css-1kpebx{margin:0 auto;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-family:nyt-cheltenham,georgia,’times new roman’,times,serif;font-weight:700;font-size:1.375rem;line-height:1.625rem;}@media (min-width:740px){#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-1kpebx{font-size:1.25rem;line-height:1.4375rem;}}.css-1gtxqqv{margin-bottom:0;}.css-k59gj9{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;width:100%;}.css-1e2usoh{font-family:inherit;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-box-pack:justify;-webkit-justify-content:space-between;-ms-flex-pack:justify;justify-content:space-between;border-top:1px solid #ccc;padding:10px 0px 10px 0px;background-color:#fff;}.css-1jz6h6z{font-family:inherit;font-weight:bold;font-size:1rem;line-height:1.5rem;text-align:left;}.css-1t412wb{box-sizing:border-box;margin:8px 15px 0px 15px;cursor:pointer;}.css-hhzar2{-webkit-transition:-webkit-transform ease 0.5s;-webkit-transition:transform ease 0.5s;transition:transform ease 0.5s;}.css-t54hv4{-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-1r2j9qz{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-e1ipqs{font-size:1rem;line-height:1.5rem;padding:0px 30px 0px 0px;}.css-e1ipqs a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;}.css-e1ipqs a:hover{-webkit-text-decoration:none;text-decoration:none;}.css-1o76pdf{visibility:show;height:100%;padding-bottom:20px;}.css-1sw9s96{visibility:hidden;height:0px;}.css-1in8jot{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;font-family:’nyt-franklin’,arial,helvetica,sans-serif;text-align:left;}@media (min-width:740px){.css-1in8jot{padding:20px;width:100%;}}.css-1in8jot:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1in8jot{border:none;padding:10px 0 0;border-top:2px solid #121212;}What to Know About Covid-19 Booster ShotsThe F.D.A. has authorized booster shots for millions of recipients of the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines. Pfizer and Moderna recipients who are eligible for a booster include people 65 and older, and younger adults at high risk of severe Covid-19 because of medical conditions or where they work. Eligible Pfizer and Moderna recipients can get a booster at least six months after their second dose. All Johnson & Johnson recipients will be eligible for a second shot at least two months after the first.Yes. The F.D.A. has updated its authorizations to allow medical providers to boost people with a different vaccine than the one they initially received, a strategy known as “mix and match.” Whether you received Moderna, Johnson & Johnson or Pfizer-BioNTech, you may receive a booster of any other vaccine. Regulators have not recommended any one vaccine over another as a booster. They have also remained silent on whether it is preferable to stick with the same vaccine when possible.The C.D.C. has said the conditions that qualify a person for a booster shot include: hypertension and heart disease; diabetes or obesity; cancer or blood disorders; weakened immune system; chronic lung, kidney or liver disease; dementia and certain disabilities. Pregnant women and current and former smokers are also eligible.The F.D.A. authorized boosters for workers whose jobs put them at high risk of exposure to potentially infectious people. The C.D.C. says that group includes: emergency medical workers; education workers; food and agriculture workers; manufacturing workers; corrections workers; U.S. Postal Service workers; public transit workers; grocery store workers.Yes. The C.D.C. says the Covid vaccine may be administered without regard to the timing of other vaccines, and many pharmacy sites are allowing people to schedule a flu shot at the same time as a booster dose.“I don’t think we ever see 100 percent protection from any vaccine,” Dr. Kotton said. “The goal of getting to zero is an evanescent one and, unfortunately, not really achievable.”“People are using it because they’re so anxious about Covid, and anxious about the state of affairs in the world,” she added, referring to booster shots.President Biden receiving a booster shot last month. Some experts said that final recommendations for boosters were inevitable as soon as Mr. Biden promised them to all adults.Doug Mills/The New York TimesGenerally, scientists on the two committees are asked to vote yes or no on questions posed to them by the federal agencies they are advising. In some cases, committee members said they voted one way or another simply because of the way those questions were phrased.In December, when F.D.A. advisers evaluated the Pfizer-BioNTech vaccine for people ages 16 and older, the evidence for its use in 16- and 17-year-olds was limited.Dr. Archana Chatterjee and three other committee members voted against the vaccine and were criticized for it. But Dr. Chatterjee said she would have voted differently if the F.D.A. had asked about authorizing the vaccine in adults 18 and older.“We were basically told, ‘Here’s the question, and say yes or no,’” said Dr. Chatterjee, a pediatric infectious disease expert and dean of the Chicago Medical School. “We were also not given the opportunity to explain the vote.”In subsequent meetings, the F.D.A. allowed the science advisers to request changes to the question and to explain their votes. But they are still restricted to voting only on the data included in a company’s application.At a recent meeting, for example, some F.D.A. advisers said they wanted to recommend that Johnson & Johnson recipients have the option to choose any vaccine for their booster. But the F.D.A. only asked the panel to vote on a booster of the Johnson & Johnson vaccine.One of the panelists, Dr. Stanley Perlman, said he voted yes because it was clear that Johnson & Johnson recipients would benefit from a second shot. But the unanimous vote signaled far more confidence in the Johnson & Johnson vaccine as a booster than he felt, said Dr. Perlman, an immunologist and coronavirus expert at the University of Iowa.Dr. Perlman said he was opposed to boosters for younger people at first, but voted in favor for other reasons. In the case of health care workers, for example, “I didn’t want to have any nurses or doctors staying home because they had asymptomatic” infections, he said.Several experts said they have tried to be clear about the limitations of the data and the rationale behind their decisions. But communicating in the midst of a pandemic has proved to be tricky.“Through no intentional fault of anyone, the messaging has been challenging — and then there’s a lot of misinformation, which is tragic,” Dr. Kotton said.In approving the boosters, however reluctantly, federal agencies and their advisers may have given Americans the impression that two doses were not protective enough, some experts said.“They continue inadvertently to damn the vaccine, when what they should say is, ‘It is remarkable,’” said Dr. Offit. “It’s a miracle vaccine.”