Americans with a disability were more likely to want coronavirus vaccines but were having a harder time getting them than other people, according to data released on Thursday by the Centers for Disease Control and Prevention, a stark signal of what the agency’s scientists said was a need for health officials to remove barriers to access.In a survey of nearly 57,000 people from May to June, unvaccinated people with a disability such as serious difficulty seeing, hearing or walking were nearly twice as likely as their unvaccinated counterparts without a disability to say that they would definitely get vaccinated. (The survey only included people outside of nursing homes and other institutions.)And yet, people with a disability were less likely to be vaccinated: Among 50- to 64-year-olds, 63 percent of people with a disability had received coronavirus shots, compared with 72 percent of other people. Among people older than 75, the gap was smaller but still evident: Eighty-eight percent of people with a disability were vaccinated, compared with 90 percent of people without one.“Covid-19 vaccination coverage was lower among U.S. adults with a disability than among those without a disability, even though adults with a disability reported less hesitancy to getting vaccinated,” the study’s authors wrote.The study noted that state-run vaccine registration websites were not all compliant with basic accessibility recommendations. It suggested that online scheduling systems offer call lines for people who needed help booking vaccinations.It also said that not all vaccination sites had American Sign Language interpreters or workers trained in helping people with developmental disabilities, and that getting to those sites in the first place was often difficult for people with a disability.“These efforts would be relevant to the reduction of health disparities related to disability beyond the Covid-19 pandemic,” the study said.

Americans who received a third dose of a coronavirus vaccine in recent weeks reported side effects at roughly the same rates as they had after their second shots, the Centers for Disease Control and Prevention said on Tuesday, a reassuring sign about the safety of additional doses.At the time of the C.D.C. study, which stretched from mid-August to mid-September, additional vaccine doses were only authorized for people with compromised immune systems who had gotten two doses of the Pfizer-BioNTech or Moderna vaccine. Last week, though, federal regulators authorized Pfizer booster shots for broad swaths of the general population, making the safety of the additional doses an issue of intense interest for health officials, doctors and ordinary Americans.The C.D.C. analyzed how commonly people reported side effects after a third dose compared with a second among 12,600 recipients who had filled out surveys as part of a voluntary safety monitoring system.Reactions at the injection site, like pain or swelling, were reported by 79.4 percent of recipients after a third vaccine dose, compared with 77.6 percent after a second dose. Slightly smaller numbers of people experienced systemic reactions, like a fever or headache: 74.1 percent of people reported those side effects after dose three, compared with 76.5 percent after dose two.“Most reported local and systemic reactions were mild to moderate, transient, and most frequently reported the day after vaccination,” the study’s authors said.The study focused on people who had received a third dose of the same vaccine that they had originally received, either from Pfizer-BioNTech or Moderna. The C.D.C. said that too few people had reported receiving an additional dose of the Johnson & Johnson vaccine, or an additional dose from a different vaccine maker than they had originally received, to study those side effects.The results reinforced findings from a small clinical trial of third shots of the Pfizer vaccine that the company’s scientists outlined to federal medical advisers last week. That trial, too, found that adverse reactions after a third dose were similar to those after a second.While the C.D.C. study covered only a period when people with immune problems were eligible for additional doses, the data likely also included people without such conditions who had nevertheless received a third shot, the study’s authors wrote. In all, the study said, about 2.2 million people had received additional doses by Sept. 19, the end of the C.D.C. study period.

When President Biden announced in June that the United States would buy 500 million Pfizer-BioNTech coronavirus vaccine doses for poorer nations, there was a gaping hole in his plan: To fund it, the administration quietly diverted hundreds of millions of dollars that had already been promised to countries for helping to get shots into people’s arms.Mr. Biden did not make the same mistake a second time.His announcement on Wednesday that the United States was donating an additional 500 million Pfizer doses came paired with a promise of an additional $750 million for vaccine distribution, roughly half of it through a nonprofit involved in global vaccinations. That reflected a growing awareness on the part of global leaders that turning vaccines into actual vaccinations represents one of the most significant challenges of this phase of the pandemic.Even so, the Biden administration’s schedule for shipping the newly announced Pfizer doses frustrated activists: Of the 1.1 billion doses that the United States has committed to donations, only 300 million are expected to be shipped this year. The longer the virus circulates around the world, the more dangerous it can become, even for vaccinated people in wealthy countries, scientists have warned.“Purchasing doses for donation sometime next year is helpful, but it does not meaningfully expand the global supply, and it is not justice,” said Peter Maybarduk, the director of the Access to Medicines program at Public Citizen, an advocacy organization.Some experts pleaded for more aggressive action by Mr. Biden to pressure American vaccine makers to share their formulas with nations that desperately need more shots.“Where is the monthly calendar of what each wealthy country is going to deliver?” said Kate Elder, senior vaccines policy adviser for Doctors Without Borders’ Access Campaign. She added, “Where are the announcements about meeting the calls of regions and middle-income countries that are begging to be self-sufficient?”It was not immediately clear how the administration was planning to allocate the new money for vaccine distributions. Some countries have been struggling to train and pay vaccinators and to transport doses. Pfizer doses present especially steep challenges: They must be stored at ultralow temperatures, requiring the installation of freezers and, in many cases, backup generators.Early this year, supply shortages represented the most pressing problem for global vaccinations. Rich nations had raced to secure doses while slow-walking pledges of money and supplies to Covax, the United Nations-backed program to immunize the world.But as those manufacturing difficulties have eased, different problems emerged. One was blatant inequality: More than 5.9 billion shots have been given globally, but overwhelmingly in wealthier nations. Another was that poorer countries had been left without the money needed to move shots from airport tarmacs into people’s arms.Although the Biden administration’s pledges have outpaced those of most Western nations, analysts said other wealthy countries were setting an extraordinarily low bar..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-w739ur{margin:0 auto 5px;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-w739ur{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-w739ur{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-w739ur{font-size:1.25rem;line-height:1.4375rem;}}.css-9s9ecg{margin-bottom:15px;}.css-16ed7iq{width:100%;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;-webkit-box-pack:center;-webkit-justify-content:center;-ms-flex-pack:center;justify-content:center;padding:10px 0;background-color:white;}.css-pmm6ed{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;}.css-pmm6ed > :not(:first-child){margin-left:5px;}.css-5gimkt{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.8125rem;font-weight:700;-webkit-letter-spacing:0.03em;-moz-letter-spacing:0.03em;-ms-letter-spacing:0.03em;letter-spacing:0.03em;text-transform:uppercase;color:#333;}.css-5gimkt:after{content:’Collapse’;}.css-rdoyk0{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-eb027h{max-height:5000px;-webkit-transition:max-height 0.5s ease;transition:max-height 0.5s ease;}.css-6mllg9{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;position:relative;opacity:0;}.css-6mllg9:before{content:”;background-image:linear-gradient(180deg,transparent,#ffffff);background-image:-webkit-linear-gradient(270deg,rgba(255,255,255,0),#ffffff);height:80px;width:100%;position:absolute;bottom:0px;pointer-events:none;}.css-uf1ume{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;}.css-wxi1cx{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-self:flex-end;-ms-flex-item-align:end;align-self:flex-end;}.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;}And even as countries have promised to donate more doses, they have been slow to follow through, with the World Health Organization saying that only 15 percent of promised donations have been delivered. The W.H.O. has set a target of vaccinating 40 percent of every country’s population this year, requiring wealthy nations to share doses significantly more quickly.There remains considerable excess supply: Wealthy nations will have 1 billion more vaccines than they need by the end of 2021, even if they administer booster shots, according to Airfinity, a science analytics company.Global health officials have urged wealthy nations to let go of those supplies before they expire. Some countries have donated vaccines so close to their expiration dates, and in such small quantities, that poorer countries have struggled to use them.Some 11 billion doses are needed globally, and activists said on Wednesday that the wealthy world’s response remained far too piecemeal. The new Pfizer doses purchased by the U.S. will be shipped through Covax starting in January.

The Centers for Disease Control and Prevention released data on Friday indicating that the level of protection against Covid hospitalizations afforded by the Pfizer-BioNTech vaccine dropped significantly in the four months after full inoculation.The data was released hours before a scientific advisory committee to the Food and Drug Administration recommended authorizing booster shots for recipients of the Pfizer coronavirus vaccine who are 65 or older or are at high risk of severe Covid-19, at least six months after the second shot.The new study found that from two weeks after recipients got their second dose — a point at which they are normally considered fully vaccinated — to four months later, the Pfizer vaccine was 91 percent effective in preventing hospitalization. Beyond 120 days, though, its effectiveness fell to 77 percent.The Moderna vaccine showed no comparable decrease in protection over the same time frame: It was 92 percent effective against hospitalizations four months after recipients’ vaccination, a level virtually identical to its 93 percent effectiveness before then.The study said that not enough participants had received the one-shot Johnson & Johnson vaccine to compare its performance. Overall, though, the Johnson & Johnson shot has been 71 percent effective in preventing hospitalizations.The C.D.C. study released on Friday supported some others that suggested the Pfizer vaccine may offer less protection from hospitalization over time. But the available data is far from unanimous. Other studies have shown that Pfizer’s effectiveness against hospitalization has remained above 90 percent, despite the spread of the Delta variant and the lengthening time since people received their second shots. Pfizer has said that data from Israel suggest a falling effectiveness against severe disease, though it appears that Israel and the United States define “severe disease” differently.The latest C.D.C. study was based on an analysis of roughly 3,700 adults hospitalized across the United States from March to August.People with compromised immune systems, who typically don’t respond as well to vaccines, were excluded from the study. Nevertheless, the vaccinated patients tended to be older people — the Pfizer cohort had a median age of 68 — and it was unclear whether vaccine effectiveness had changed much in younger age groups. Previous studies have shown lower levels of protection in older people.The authors of the study said that the gap in the performance of the Moderna and Pfizer vaccines could stem from higher doses of mRNA in the Moderna shots or the four-week space between doses of the Moderna vaccine. (Pfizer vaccines were given three weeks apart.) It’s also possible, they said, that other, unnoticed differences in the study participants receiving either shot could have also influenced the results.

Championed by doctors and conservative radio hosts alike, monoclonal antibodies for Covid are in high demand — even from those who don’t want a vaccine.Lanson Jones did not think that the coronavirus would come for him. An avid tennis player in Houston who had not caught so much as a cold during the pandemic, he had refused a vaccine because he worried that it would spoil his streak of good health.But contracting Covid shattered his faith in his body’s defenses — so much so that Mr. Jones, nose clogged and appetite vanished, began hunting for anything to spare himself a nightmarish illness.The answer turned out to be monoclonal antibodies, a year-old, laboratory-created drug no less experimental than the vaccine. In a glass-walled enclosure at Houston Methodist Hospital this month, Mr. Jones, 65, became one of more than a million patients, including Donald J. Trump and Joe Rogan, to receive an antibody infusion as the virus has battered the United States.Vaccine-resistant Americans are turning to the treatment with a zeal that has, at times, mystified their doctors, chasing down lengthy infusions after rejecting vaccines that cost one-hundredth as much. Orders have exploded so quickly this summer — to 168,000 doses per week in late August, up from 27,000 in July — that the Biden administration warned states this week of a dwindling national supply.The federal government, which was already covering the cost of the treatment — currently about $2,100 per dose — has now taken over its distribution as well. For the coming weeks, the government has told states to expect scaled-back shipments because of the looming shortages.With seven Southern states accounting for 70 percent of orders, the new process has unsettled some of their governors, who have made the antibody treatment central to their strategy for enduring a catastrophic wave of the Delta variant.More supplies are on the way. The federal government bought 1.8 million more doses this week, expected to arrive in the fall and winter. But for now, some hospitals are uncertain of supplies, state health officials said, even as patients keep searching for doses.“We have providers struggling to get the necessary product,” Kody Kinsley, who leads operations for North Carolina’s Covid-19 response, said in an interview. “I think what has happened is a classic logistics issue, where all of a sudden there’s much more demand.”Amid a din of antivaccine falsehoods, monoclonal antibodies have become the rare coronavirus medicine to achieve near-universal acceptance. Championed by mainstream doctors and conservative radio hosts alike, the infusions have kept the country’s death toll — 2,000 per day and climbing — from soaring even higher.And after months of work by President Biden and Southern governors to promote the treatments, they have won the affection of vaccine refusers who said that the terrors and uncertainties of actually getting Covid had made them desperate for an antidote.“The people you love, you trust, nobody said anything negative about it,” Mr. Jones said of the antibody treatment. “And I’ve heard nothing but negative things about the side effects of the vaccine and how quickly it was developed.”Lanson Jones, a landscape architect in Houston, recovered quickly from Covid after receiving monoclonal antibodies.Brandon Thibodeaux for The New York TimesSome Republican governors have set up antibody clinics while opposing vaccine mandates, frustrating even some of the drugs’ strongest proponents. Raising vaccination rates, scientists said, would obviate the need for many of the costly antibody treatments in the first place. The infusions take about an hour and a half, including monitoring afterward, and require constant attention from nurses whom hard-hit states often cannot spare.“It’s clogging up resources, it’s hard to give, and a vaccine is $20 and could prevent almost all of that,” said Dr. Christian Ramers, an infectious disease specialist and the chief of population health at Family Health Centers of San Diego, a community-based provider. Pushing antibodies while playing down vaccines, he said, was “like investing in car insurance without investing in brakes.”The government-supplied monoclonal antibodies, made by Regeneron and Eli Lilly, have been shown to significantly shorten patients’ symptoms and reduce their risk of being hospitalized — by 70 percent, in the case of Regeneron’s antibody cocktail. The treatments, given in a single sitting, use lab-made copies of the antibodies that people generate naturally when fighting an infection.Patients and doctors alike overlooked the treatments during the wintertime surge of infections. But hospitals and health centers have now ramped up their offerings, transforming dental clinics, mobile units and auditoriums into infusion centers. In states like Texas, where elective surgeries have been postponed to make room for Covid-19 patients, operating room nurses have been enlisted to give infusions.One factor driving the demand is that many patients, including vaccine skeptics, have been spreading the word about their seemingly miraculous recoveries.“They’re like, ‘I have Covid, I want this treatment, my friend or family told me about this,’” said Jennifer Berry, the Houston Methodist nursing director of infusion services. “Now the word is out.”At Houston Methodist, nurses administered nearly 1,100 treatments across eight sites in the first week of September, well more than twice as many as any week last winter. The hospital reduced the average time between orders and infusions to two days this month from three days in early August, giving patients a better chance of fighting off infections.Juggling the infusions with more seriously ill Covid patients this summer forced the hospital, in one case, to move a monoclonal antibody clinic to a strip mall storefront.But the Texas health department has helped, providing 19 nurses for a different Houston Methodist infusion clinic, said Vicki Brownewell, the lead administrator for the hospital’s program. The Biden administration has also invested $150 million in expanding access to monoclonal antibodies, and Houston Methodist has used federal money to arrange medical taxis for patients struggling with transportation.Antibody infusions at Houston Methodist earlier this week. Of the 2.4 million monoclonal antibody doses shipped nationally, at least 1.1 million have been used.Brandon Thibodeaux for The New York TimesEven so, the infusions remain inaccessible to many. Given the heavy demands on staff and the need to create separate infusion rooms for infectious patients, certain communities, especially in rural areas, do not have clinics.In San Diego, Dr. Ramers said, some large, for-profit hospitals have decided not to administer the antibodies at all because of the logistical hassles, leaving wealthier, well-insured patients to hunt down doses at his publicly funded clinic. Some nurses that he hired for infusions left for short, better-paying assignments in hard-hit intensive care units.“The natural, capitalist incentives for health care organizations that are for profit don’t really favor doing this,” Dr. Ramers said. “It’s a lot of work.”.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-w739ur{margin:0 auto 5px;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-w739ur{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-w739ur{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-w739ur{font-size:1.25rem;line-height:1.4375rem;}}.css-9s9ecg{margin-bottom:15px;}.css-16ed7iq{width:100%;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;-webkit-box-pack:center;-webkit-justify-content:center;-ms-flex-pack:center;justify-content:center;padding:10px 0;background-color:white;}.css-pmm6ed{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;}.css-pmm6ed > :not(:first-child){margin-left:5px;}.css-5gimkt{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.8125rem;font-weight:700;-webkit-letter-spacing:0.03em;-moz-letter-spacing:0.03em;-ms-letter-spacing:0.03em;letter-spacing:0.03em;text-transform:uppercase;color:#333;}.css-5gimkt:after{content:’Collapse’;}.css-rdoyk0{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-eb027h{max-height:5000px;-webkit-transition:max-height 0.5s ease;transition:max-height 0.5s ease;}.css-6mllg9{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;position:relative;opacity:0;}.css-6mllg9:before{content:”;background-image:linear-gradient(180deg,transparent,#ffffff);background-image:-webkit-linear-gradient(270deg,rgba(255,255,255,0),#ffffff);height:80px;width:100%;position:absolute;bottom:0px;pointer-events:none;}.css-uf1ume{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;}.css-wxi1cx{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-self:flex-end;-ms-flex-item-align:end;align-self:flex-end;}.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;}Of the 2.4 million monoclonal antibody doses shipped nationally, at least 1.1 million have been used. Precisely how many are still sitting on shelves is hard to determine because of reporting gaps. Still, waning federal supplies and soaring demand from less-vaccinated Southern states have caused what several states have described as large shortfalls in deliveries.North Carolina providers have requested 15,000 weekly doses, the health department there said, more than double what the federal government has allocated. Florida said its latest weekly allotment left clinics there 41,000 doses short of what they wanted.Hospitals had previously been able to order the drugs themselves. But the Department of Health and Human Services will now decide how many doses each state receives based on case rates and use of the treatment. State governments, in turn, will decide on doses for individual sites.The new ordering process, which the Biden administration said would ensure “equitable distribution,” has unsettled some backers of the drug. Gov. Ron DeSantis of Florida, a Republican, warned on Thursday that state officials were unprepared for the new responsibility of parceling out doses.And in heavily vaccinated states, like New York, people coordinating treatments fear that shipments will plummet because of low case rates, leaving hospitals with so few doses that they shutter their programs. Some hospitals recently reported growing numbers of vaccinated patients receiving infusions.Diana Berrent, the founder of Survivor Corps, which has worked to help patients find monoclonal antibody treatments, said that involving state governments would create delays: “You’re layering in 50 new layers of bureaucracy,” she said.Dr. Howard Huang, Houston Methodist’s medical leader for the infusion program.Brandon Thibodeaux for The New York TimesDoctors have warned that antibody treatments alone cannot keep pace with ballooning outbreaks. Whereas any one vaccination protects untold others from exposure, a single infusion only helps a single patient. Infusions must be given within 10 days of symptoms; they are unhelpful to most hospitalized patients. And receiving the antibodies once does not keep people from becoming seriously ill if they catch the virus again later.“Something like that just doesn’t scale,” said Dr. Howard Huang, the medical leader for Houston Methodist’s infusion program.As a result, health officials have warned that vaccine skeptics may become so enamored of monoclonal antibodies that they become even more resistant to getting a protective shot.Within days of his infusion, Mr. Jones, the patient in Houston, had left the bedroom where he had been quarantined and returned to his work as a landscape architect. But he was still weighing whether to be vaccinated.His doctor was pushing for the shot, he said. But the monoclonal antibodies had worked so well that he was tempted to simply return for another infusion if he caught Covid-19 again.“If I can go get an infusion and feel as good as I do right now, man, I’d rather not take a vaccine that has just been developed,” he said. “That makes me nervous, still.”Rebecca Robbins contributed reporting.

The largest published study to date of certain post-vaccine side effects found that people were at slightly higher than normal risk of blood clots after receiving an AstraZeneca or Pfizer-BioNTech shot. But the same clotting conditions were substantially more likely to occur — and over longer periods — among people infected with the coronavirus, the study found.Coupled with another study this week from Israel, the data, published on Thursday night in The British Medical Journal, added to the growing evidence that though the coronavirus vaccines are associated with certain rare side effects, those risks are dwarfed by the risks from Covid-19.The study was based on the electronic health records of more than 29 million people in England. It went beyond previous analyses in finding a link not only between very rare clotting conditions and the AstraZeneca vaccine, but also between those conditions and the Pfizer vaccine. Earlier studies had detected increased clotting risks after the AstraZeneca vaccine, but not after the Pfizer shot.In interviews, the new paper’s co-authors said that the numbers of those cases they detected — involving clots blocking a vein that drains blood from the brain — were small enough that further studies were needed. Even the increased risk of those clots was far outweighed by people’s chances of developing them after contracting the virus itself, the study said.“Although there are some risks, clearly the risks of these events are very rare,” said Aziz Sheikh, a co-author of the study and a professor of primary care research at the University of Edinburgh in Scotland. “And the biggest point is that the risks associated with Covid-19 are orders of magnitude higher, really.”The study examined the electronic health records of people given a first dose of a coronavirus vaccine during the first five months of England’s inoculation campaign. Of those 29 million people, nearly 1.8 million people also tested positive for the coronavirus before or after being vaccinated. The study compared the risk of blood clots shortly after vaccination to the risk during other periods, as well as to the weeks after someone developed Covid-19.After a first shot of the AstraZeneca vaccine, people were at slightly increased risk of certain blood clots, as well as a condition characterized by a low level of platelets that can leave them prone to abnormal bleeding. A first shot of the Pfizer vaccine appeared to put people at slightly elevated risk of strokes caused by blockages within a blood vessel.And both vaccines were linked, though at low numbers, to the very rare clots that prevent blood from draining out of the brain.Even so, those risks were far smaller than those linked to developing Covid-19. For example, the authors said, for every 10 million people given a first dose of the AstraZeneca vaccine, about 66 more people than normal would develop clots starting in a vein. But among the same number infected with the virus itself, 12,614 more people than normal would develop those clots.In the United States, 300,000 to 600,000 people a year develop blood clots in their lungs or in leg veins or other parts of the body, according to the C.D.C. With nearly a million people a day now getting vaccinated, some of those clots will occur in those receiving the shots just by coincidence, unrelated to the vaccine..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-w739ur{margin:0 auto 5px;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-w739ur{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-w739ur{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-w739ur{font-size:1.25rem;line-height:1.4375rem;}}.css-9s9ecg{margin-bottom:15px;}.css-16ed7iq{width:100%;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;-webkit-box-pack:center;-webkit-justify-content:center;-ms-flex-pack:center;justify-content:center;padding:10px 0;background-color:white;}.css-pmm6ed{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;}.css-pmm6ed > :not(:first-child){margin-left:5px;}.css-5gimkt{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.8125rem;font-weight:700;-webkit-letter-spacing:0.03em;-moz-letter-spacing:0.03em;-ms-letter-spacing:0.03em;letter-spacing:0.03em;text-transform:uppercase;color:#333;}.css-5gimkt:after{content:’Collapse’;}.css-rdoyk0{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-eb027h{max-height:5000px;-webkit-transition:max-height 0.5s ease;transition:max-height 0.5s ease;}.css-6mllg9{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;position:relative;opacity:0;}.css-6mllg9:before{content:”;background-image:linear-gradient(180deg,transparent,#ffffff);background-image:-webkit-linear-gradient(270deg,rgba(255,255,255,0),#ffffff);height:80px;width:100%;position:absolute;bottom:0px;pointer-events:none;}.css-uf1ume{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;}.css-wxi1cx{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-self:flex-end;-ms-flex-item-align:end;align-self:flex-end;}.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;}Some countries restricted use of the AstraZeneca vaccine after a small number of people in Europe who had received a shot were seriously sickened or killed by a very rare condition characterized by both clotting and abnormal bleeding.Carol Coupland, a co-author on the latest study and a professor of medical statistics affiliated with both the University of Oxford and the University of Nottingham, said that the study could not evaluate that precise condition because the researchers did not have detailed enough readings of patients’ platelet counts.The finding of a slightly elevated clotting risk after the Pfizer vaccine conflicted with other analyses, including the article from Israel published in the New England Journal of Medicine this week. The study from England included far more people, allowing it to home in on rarer categories of clots. It was also designed differently: It studied the same people over time, whereas the Israeli study compared risks in vaccinated and unvaccinated people over the same period.Ben Reis, a co-author of the Israeli study and the director of the predictive medicine group at the Boston Children’s Hospital Computational Health Informatics Program, said that both studies were a testament to the way electronic health records allowed researchers to rapidly pick up on even very rare safety signals and compare the risks to those following a coronavirus infection.“The vaccination decision shouldn’t be made in a vacuum,” he said. “The alternative outcome is the very real risk of being exposed to the virus without vaccination. Those are the two scenarios that should be compared.”

If you haven’t yet mastered the name of the latest coronavirus variant to set nations on edge — B.1.617.2, as evolutionary biologists call it — then fear not: The World Health Organization has proposed a solution.The group said on Monday that it had devised a less technical, and more easily pronounceable, system for naming variants — the mutated versions of the virus that have driven new surges of infections around the world.Variants will be assigned letters of the Greek alphabet in the order in which they are designated potential threats by the W.H.O.B.1.617.2, for example, which has contributed to a deadly surge in India, has been named Delta under the new system. That variant may spread even more quickly than B.1.1.7, the variant discovered in Britain that has contributed to devastating waves of cases globally. (B.1.1.7’s new name is Alpha.)Scientists will keep assigning long strings of letters and numbers to new variants for their own purposes, but they hope that Greek letters will roll off the tongues of nonscientists more easily.There is also a deeper motivation: The letters-and-numbers system was so complicated that many people were referring to variants by the places they were discovered instead (“the Indian variant” for B.1.617.2, for example). Scientists worry that those informal nicknames can be both inaccurate and stigmatizing, punishing countries for investing in the genome sequencing necessary to sound an alarm about new mutations that may well have emerged somewhere else.Whether the Greek letters will stick is another matter. It has been months since experts convened by the W.H.O. began discussing the issue, allowing labels like “the British variant” and “the South African variant” to proliferate in the news media.The experts said they had considered a number of alternatives, like taking syllables from existing words to make new words. But too many of those syllable combinations were already recognizable names of places or businesses, they said.And as it happens, the Greek letters had just been freed up from another task: The World Meteorological Organization said in March that it would no longer use them to name hurricanes.

Amid a deep residue of mistrust, Western cautions on the AstraZeneca and Johnson & Johnson vaccines risk igniting an explosion of damaging anti-vaccine fervor in the global south.Far beyond the United States and Europe, the safety scares engulfing the AstraZeneca and Johnson & Johnson vaccines have jeopardized campaigns to inoculate the world, undercutting faith in two sorely needed shots and threatening to prolong the coronavirus pandemic in countries that can ill afford to be choosy about vaccines.With new infections surging on nearly every continent, signs that the vaccination drive is in peril are emerging, most disconcertingly in Africa.In Malawi, people are asking doctors how to expunge the AstraZeneca vaccine from their bodies.In South Africa, health officials have paused giving the Johnson & Johnson shot, the only one they have, a repeat blow after dropping AstraZeneca from their arsenal in February.And in the Democratic Republic of Congo, not a single person has been vaccinated, despite 1.7 million doses of the AstraZeneca shot languishing in the country since March 2.In those countries and others, Western colonialism and unethical medical practices have left a residue of mistrust in vaccines, which could harden if the perception takes hold that rich countries are dumping second-rate shots on the global south.Already, doctors say, the recent pauses have vindicated vaccine skeptics and made many others feel duped.“People, especially those who were vaccinated, felt like they had been tricked in a way — they were asking, ‘How do we get rid of the vaccine in our body?’” said Precious Makiyi, a doctor and behavioral scientist in Malawi, where health workers have been racing to empty their shelves of nearly expired AstraZeneca doses. “We fought so hard with vaccine messaging, but what has happened this past week has brought us back to square zero.”Police officers guarding AstraZeneca vaccines after a shipment arrived last month in Lilongwe, the capital of Malawi.Thoko Chikondi/Associated PressAfrican health officials have reacted with fury at the breezy reassurances of American and European lawmakers that people denied the AstraZeneca or Johnson & Johnson shots could be given another vaccine. In much of the world, there are no other vaccines.And even as American health officials stressed that they paused use of the Johnson & Johnson vaccine on Tuesday in “an abundance of caution,” they forced global health officials to begin crafting the difficult case that shots unsafe for the world’s rich were still suited to its poor. “It’s sending vaccine confidence into a crater,” Ayoade Alakija, co-chair of the African Union’s Africa Vaccine Delivery Alliance, said of rich countries’ actions. “It’s irresponsible messaging, and it speaks to the selfishness of the moment that there wouldn’t be more consultation and communication.”What rich countries call caution, poorer nations will experience as a devastating gamble with the survival of their citizens against Covid-19. “Out of an abundance of caution, let us not destroy vaccine confidence in places that only have access to one type of vaccine,” Dr. Alakija said.The AstraZeneca and Johnson & Johnson vaccines, cheaper and easier to store than the alternatives, are mainstays of global inoculations. AstraZeneca’s shot is being used in at least 118 countries. Lately, amid shortages of that vaccine, some regions have pivoted to Johnson & Johnson’s: Two weeks ago, the African Union acquired 400 million doses.Together, the two vaccines account for a third of the portfolio of Covax, the international effort to procure and distribute vaccines.But it is becoming more apparent by the day that those shots, built on a relatively rugged vaccine platform, are becoming afterthoughts in wealthy nations. After canceling Johnson & Johnson appointments over concerns about rare blood clots, American states offered people the pricier Pfizer or Moderna vaccines instead. The European Union said on Wednesday that it had acquired another 50 million doses of the Pfizer vaccine, allowing it to curb use of AstraZeneca’s vaccine and phase it out altogether next year.Those decisions, intended for domestic audiences, have nevertheless reverberated in countries where variants are spreading, physical distancing is a luxury and there is no choice of shots. Health officials fear that any setbacks in vaccinations could sow the seeds of the next calamitous outbreak, one that deluges hospitals and exports new mutations around the world. In those places, doctors said, the math is obvious: Many more people will die without the AstraZeneca and Johnson & Johnson vaccines than with them.Amid the clotting concerns, the World Health Organization and African Union have not wavered in recommending the use of the AstraZeneca and Johnson & Johnson’s vaccines. In Britain, AstraZeneca’s vaccine remains the backbone of the country’s speedy inoculation campaign, despite people under 30 being offered alternatives. Congo, after spurning the AstraZeneca shot in light of unease in Europe, said on Tuesday that it would launch the much-delayed inoculations next week.A vaccination center inside Salisbury Cathedral, in Salisbury, England, in January. Britain has forged ahead with the AstraZeneca vaccine, though restricting its use to people aged 30 and above.Andrew Testa for The New York TimesAnd in Dakar, the capital of Senegal, people continued to line up on wooden benches on Wednesday for the AstraZeneca shot as they watched their children run through the corridors of a medical center.“We don’t have a choice,” said Alioune Badara Diagne, 34, who lives in the city’s lively Ouakam neighborhood. Despite talk of vaccination pauses in wealthy nations and rumors of vaccine makers using Africans as “guinea pigs,” he said, Westerners themselves were continuing to be injected. He added, “The vaccine is our only hope.”But in much of the world, the American regulators who endorsed Tuesday’s pause on Johnson & Johnson vaccinations act as sort of surrogate decision makers on drugs and vaccines, giving their hesitation extra weight in African nations.“I became even more skeptical when I heard that the United States suspended Johnson & Johnson,” said Lawmond Lawse Nwehla, 32, an engineer in Dakar. “They said it was effective and then they stopped it. So I wonder why.”In immediately pausing the use of Johnson & Johnson’s shot, American regulators reacted more aggressively than did their British counterparts, who backed the AstraZeneca vaccine even as they investigated clotting cases..css-1xzcza9{list-style-type:disc;padding-inline-start:1em;}.css-rqynmc{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.9375rem;line-height:1.25rem;color:#333;margin-bottom:0.78125rem;}@media (min-width:740px){.css-rqynmc{font-size:1.0625rem;line-height:1.5rem;margin-bottom:0.9375rem;}}.css-rqynmc strong{font-weight:600;}.css-rqynmc em{font-style:italic;}.css-yoay6m{margin:0 auto 5px;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}@media (min-width:740px){.css-yoay6m{font-size:1.25rem;line-height:1.4375rem;}}.css-1dg6kl4{margin-top:5px;margin-bottom:15px;}.css-16ed7iq{width:100%;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;-webkit-box-pack:center;-webkit-justify-content:center;-ms-flex-pack:center;justify-content:center;padding:10px 0;background-color:white;}.css-pmm6ed{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;}.css-pmm6ed > :not(:first-child){margin-left:5px;}.css-5gimkt{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.8125rem;font-weight:700;-webkit-letter-spacing:0.03em;-moz-letter-spacing:0.03em;-ms-letter-spacing:0.03em;letter-spacing:0.03em;text-transform:uppercase;color:#333;}.css-5gimkt:after{content:’Collapse’;}.css-rdoyk0{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-eb027h{max-height:5000px;-webkit-transition:max-height 0.5s ease;transition:max-height 0.5s ease;}.css-6mllg9{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;position:relative;opacity:0;}.css-6mllg9:before{content:”;background-image:linear-gradient(180deg,transparent,#ffffff);background-image:-webkit-linear-gradient(270deg,rgba(255,255,255,0),#ffffff);height:80px;width:100%;position:absolute;bottom:0px;pointer-events:none;}#masthead-bar-one{display:none;}#masthead-bar-one{display:none;}.css-1pd7fgo{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-1pd7fgo{padding:20px;width:100%;}}.css-1pd7fgo:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1pd7fgo{border:none;padding:20px 0 0;border-top:1px solid #121212;}.css-1pd7fgo[data-truncated] .css-rdoyk0{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-1pd7fgo[data-truncated] .css-eb027h{max-height:300px;overflow:hidden;-webkit-transition:none;transition:none;}.css-1pd7fgo[data-truncated] .css-5gimkt:after{content:’See more’;}.css-1pd7fgo[data-truncated] .css-6mllg9{opacity:1;}.css-1rh1sk1{margin:0 auto;overflow:hidden;}.css-1rh1sk1 strong{font-weight:700;}.css-1rh1sk1 em{font-style:italic;}.css-1rh1sk1 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:#ccd9e3;text-decoration-color:#ccd9e3;}.css-1rh1sk1 a:visited{color:#333;-webkit-text-decoration-color:#ccc;text-decoration-color:#ccc;}.css-1rh1sk1 a:hover{-webkit-text-decoration:none;text-decoration:none;}The costs of the American approach were already evident in Europe, where many nations stopped and then restarted AstraZeneca vaccinations, only to find that it had become a pariah. Most people in France, Germany and Spain distrusted the vaccine.“Once you take the cork out of the bottle, I’m not sure you can get it back in particularly easily,” said Anthony Cox, a vaccines safety expert at the University of Birmingham in England. South Africa immediately copied the American pause on Johnson & Johnson vaccinations, infuriating doctors who are still clamoring for shots, especially in remote parts of the country. In February, health officials dropped the AstraZeneca vaccine over its limited efficacy against a dangerous variant there.To date, only half of 1 percent of the population is vaccinated, and a mere 10,000 shots are being given each day. At that rate, it could take weeks, if not longer, for a single rare blood clotting case to emerge, said Jeremy Nel, an infectious disease doctor in Johannesburg. He was dismayed by the decision to pause shots, given the risk to vaccine confidence in a country where two-fifths of the people say they have no intention of being vaccinated.“The slower you go, that failure is measured in death,” Dr. Nel said. “Even if you delay for a week, there is a non-trivial chance that will cost lives.”The solution in many European countries — to stop using seemingly riskier vaccines in younger people, who are at lower risk from Covid-19 — would be unworkable in Africa, where the median age in many countries is below 20.And any further restrictions would compound the hurdles facing Covax, among them a paucity of funding for every part of inoculation programs beyond the touchdown of doses at airports.Mali, in western Africa, has administered 7 percent of the AstraZeneca doses that Covax has delivered. Sudan, in eastern Africa, has given 8 percent of the doses it has received.Skittishness over the AstraZeneca and Johnson & Johnson vaccines, analysts fear, could stoke demand for Russian- and Chinese-made shots about which far less is known. As it is, some global health officials have turned their attention to the Novavax vaccine, which is not yet authorized but makes up a third of Covax’s portfolio.“Even at this stage of the pandemic, we have our fingers crossed that some vaccine will work to help vaccinate developing countries, instead of ramping up production of vaccines we know work,” said Zain Rizvi, an expert on medicines access at Public Citizen, an advocacy group.In Kenya, where enthusiasm for vaccines is high in cities but perilously low in rural areas, “the story about blood clots from Europe could not have come at a worse time,” said Catherine Kyobutungi, the director of the African Population and Health Research Center there. “Even those who were perhaps on the fence, and leaning toward getting vaccinated, all of a sudden had second thoughts,” she said.The American pause on Johnson & Johnson shots promised a second media furor.“When the F.D.A. suspends, it makes headlines for days,” she said. “When it lifts the suspension, it doesn’t make as many headlines.”Mady Camara contributed reporting from Dakar, Senegal.

The company defended its claims of 79 percent efficacy for its coronavirus shot and said it would release more up-to-date trial results within 48 hours.LONDON — The announcement this week that the AstraZeneca shot, the workhorse of global vaccine rollouts, had achieved nearly 80 percent efficacy in a gold-standard American trial was met with relief by the many countries relying on it.“When you get the call, get the jab,” the British health secretary, Matt Hancock, urged, part of a campaign by European lawmakers to calm people’s nerves after a recent safety scare with the shot.But by Tuesday, that campaign had, once again, been thrown off course, at least for the moment. For AstraZeneca, it was seemingly another episode of public relations whiplash, part of a series of recent miscues and communication blunders by the company that scientists said had undercut the effort to sell one of the most potent and indispensable vaccines against the coronavirus.In a highly unusual move, American health officials said on Tuesday that the company’s account of its U.S. trial findings had not been entirely accurate, suggesting that AstraZeneca had used only the most favorable data to generate apparently spectacular efficacy results.Those comments created new friction between AstraZeneca and American officials even as the company vies for a coveted authorization from the Food and Drug Administration. But more urgently, they threw a wrench into the efforts of elected leaders around the world to rebuild trust in a shot whose low price and easy storage requirements have made it the backbone of many countries’ campaigns to end the pandemic.“It’s eroding confidence,” said Simon Clarke, an associate professor in cellular microbiology at the University of Reading. “When you pump things up, and then people not unreasonably question it, then that erodes confidence.”A vaccination center in Belgrade, Serbia, this month. Despite troubling news reports about the AstraZeneca vaccine, European and global regulators have deemed the shots safe and effective.Laura Boushnak for The New York TimesFaith in the vaccine had already plunged across Europe after recent reports that a very small number of recipients had developed unusual blood clots. In France, Germany, Italy and Spain, more people now believe that the vaccine is unsafe than that it is safe, polling has shown, a blow to a shot that remains the continent’s best hope for saving people’s lives during a mounting surge of new infections.Despite the drumbeat of troubling news reports about the vaccine, European and global regulators have deemed it safe and effective. More than 11 million doses have been administered in Britain alone, almost all of them without serious side effects, driving down hospitalizations and helping the country to emerge from a dreadful wintertime wave of infections.Nevertheless, AstraZeneca’s U.S. trial was hotly anticipated. The largest of its kind for the shot, it had been expected to provide the cleanest, most complete picture of the vaccine’s efficacy. American officials saw it as an incontrovertible test of the vaccine’s performance.And health officials around the world were looking to it as a crucial guide to their own rollouts: It would supply crucial data on older people, who had not been as well represented in earlier trials, and a more precise read on the vaccine’s overall efficacy, which had appeared from earlier trials to be lower than that of other leading shots.As soon as AstraZeneca announced its results on Monday, saying that the vaccine had 79 percent efficacy in preventing symptomatic Covid-19, lawmakers began citing it as part of their fledgling efforts to shore up public confidence in the vaccine.Prime Minister Boris Johnson of Britain received an AstraZeneca shot on Friday. “I literally did not feel a thing,” he later said. “I cannot recommend it too highly.”Pool photo by Frank AugsteinBy Tuesday, scientists said, it seemed as though AstraZeneca had punched a hole in those efforts. Rather than sewing up questions about the shot, it had called to mind communications problems that have dogged the company since last year, delaying the regulatory process in some regions and creating hesitation among some recipients.Scientists said that such a public dust-up between the American medical experts overseeing a trial and the company sponsoring it was extremely unusual.“It is usually done in private,” Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, said of disagreements between a data and safety monitoring board — the experts overseeing the trial — and a vaccine maker. “So this is unprecedented, in my opinion.”In its first public comments, AstraZeneca said that the results published on Monday reflected its U.S. trial data up to Feb. 17. It said that its preliminary assessment of more complete trial data showed that “the results were consistent with the interim analysis,” but said that it would share more up-to-date efficacy results within 48 hours.Scientists said that the problem could yet turn out to be a technical matter that did not change their assessment of the vaccine. American officials did not suggest that any safety issues had been withheld, a subject of intense interest in the wake of the concerns in Europe.AstraZeneca said that the results published on Monday reflected its U.S. trial data up to Feb. 17.  American officials did not suggest that any safety issues had been withheld.Alessandro Grassani for The New York TimesNevertheless, it quickly took the wind out of the sails of European lawmakers’ public campaign to restore confidence in the shot. In recent days, a number of political leaders, including Prime Minister Boris Johnson of Britain and Prime Minister Jean Castex of France, have received the vaccine themselves in a bid to show people that it was safe.“I literally did not feel a thing,” Mr. Johnson told reporters. “I cannot recommend it too highly.”The stumble on Tuesday was the latest in a series of miscues that have made for a prickly relationship between AstraZeneca and American and European regulators — and, scientists said, created unnecessary public confusion about a vaccine that appears to be highly effective.In early September, the company quietly halted its global trials after a participant in Britain fell ill. But American regulators did not find out until the story broke publicly. Subsequently, the company’s slowness to provide the F.D.A. with evidence that its vaccine was not linked to any illnesses kept it grounded for nearly seven weeks. AstraZeneca has said it shared data in a timely manner.By late November, the company was again riding high: It released results from early clinical trials, including in Britain, showing that the vaccine was up to 90 percent effective.But those results, too, were quickly clouded by uncertainty. AstraZeneca later acknowledged that there had initially been confusion over the vaccine dosage received by some study participants, making it more difficult to interpret the findings.Britain, which has long championed the homegrown vaccine, authorized the shot in late December, relying on the earlier clinical trial results. The European Union’s medicine regulator did the same, but a month later.E.U. officials said that the delay had partly resulted from a back-and-forth between the regulators and AstraZeneca over the quality of the data.Waiting outside a vaccination center in Munich, Germany, on Sunday. Europe has seen a mounting surge of new infections recently.Laetitia Vancon for The New York TimesAnd even after the vaccine was authorized, a number of European countries initially restricted it to younger people, citing a lack of sufficient data about its efficacy in older people. That problem was supposed to be resolved by the American trial, in which older people were better represented.Neither European nor British regulators gave any indication on Tuesday that the problems with AstraZeneca’s American data would have any impact on rollouts there. Those agencies relied on a separate set of data from non-American trials to authorize the vaccine.“We are in contact with the company regarding this further information,” the European Medicines Agency said in a statement on Tuesday, “and E.M.A. will assess the data concerned as soon as the company submits it to us.”Matina Stevis-Gridneff contributed reporting from Brussels.