Two promising coronavirus vaccine candidates were speeding through trials in September when the country’s top public health agency invited states to submit plans describing how they would get the shots to millions of people. It was an opportunity, eight months after the United States confirmed its first coronavirus case, to redeem the nation’s devastating failures in organizing a regimen of testing, contact tracing and equipping medical workers with protective gear.

“We have the time to take the lessons learned from the last six months and apply them forward and get it right,” Soumi Saha, a pharmacist and advocate for cost-effective health care, said on that optimistic mid-September day. “The one thing we know for sure is a fragmented approach does not work.”

But that is precisely what the nation got. Health departments and hospital executives are struggling to compensate for decentralized planning, complaining that they were not given enough money to prepare for missions that are becoming increasingly urgent as the coronavirus pandemic reaches new peaks. The United States recorded more than 4,000 covid-19 deaths on a single day last week.

The story of how this happened reflects schisms that have defined the U.S. response, with mistrust smoldering between career scientists and political appointees accountable during an election year to a president widely criticized for his response to the pandemic but who took credit on the stump for vaccine development and promised one would be ready “very soon.” The delayed and disjointed vaccine rollout is the product of poor coordination between the federal government and the 50 states and additional jurisdictions tasked with carrying out the most ambitious immunization campaign in history, likened by officials to the effort to turn back the Nazis in 1944.

With these problems thwarting the rollout, it is clear the United States has not learned from its fractured pandemic response and risks repeating some of the same errors.

“My peers in infectious-disease medicine and public health are all looking around saying, ‘How are you all handling these issues? What happens when we get airdropped vaccines? Who gets it first? How do we do it equitably?’ ” said David Aronoff, director of the division of infectious diseases at Vanderbilt University Medical Center.

Late last year, Health and Human Services Secretary Alex Azar and other top administration officials spent weeks predicting that 20 million people would be immunized by the end of 2020. But by the time the New Year’s Eve Ball fell, just over 3 million doses had been administered, prompting a blast of criticism from dismayed public health officials who said the Trump administration used the vaccines’ development as a political tool in a bid to win reelection without planning sufficiently for their rollout.

Vaccine experts say the dispiriting launch reflects more than inflated estimates. The government’s decision to leave 64 states and other jurisdictions to devise individual plans spawned duplicative meetings, emails and telephone calls as local officials strained to share advice about common logistical challenges.

Since the rollout began last month, sign-up websites have crashed and long lines have snaked outside clinics, even as some people, including health-care workers, have rejected the shots out of unfounded fears about their safety — problems that veterans of immunization campaigns worldwide say could have been addressed through comprehensive, centralized planning and communication.

“All the focus was on developing the vaccines,” said Walter A. Orenstein, an epidemiologist at the Emory University School of Medicine, who was director of the U.S. Immunization Program for 16 years. “I don’t think there was enough focus on getting vaccine into the arms of the people who need them.”

In an interview, Azar defended the administration’s record, hailing the delivery of millions of vaccine doses to the nation. He and other senior administration officials said the government has worked closely with states, with final decisions about how to distribute and administer vaccine left to them rather than setting up federally run mass-immunization sites.

“It was always . . . agreed to that we needed to use and leverage existing systems of vaccine administration through the United States, with the states playing the leading role,” Azar said.

He insisted that money was not an impediment for state-run vaccination programs.

“We bought the vaccine. We’re paying for the distribution costs. We’ve kitted the syringes, needles and [personal protective equipment] for it,” he said.

Administration officials attributed the delay in administering vaccines to states and health systems too rigidly adhering to guidance about who should receive priority for shots.

As of Monday, 25.5 million doses of vaccine made by Pfizer-BioNTech and Modernahad been distributed, but barely 9 million people had received their first shot, according to a government tracker.

Delivering vaccines to millions of people in mere months was destined to hit roadblocks, and even nations with vaunted pandemic responses, such as Germany, have been bedeviled by the complexity of that effort.

Azar said in the recent interview that he and others had created unrealistic expectations that 20 million people would get vaccinated by the end of December.

“I’m going to concede to you, myself included and other senior people on TV interviews, there were a couple of instances where we accidentally used shorthand to say 20 million vaccinations [would be administered] rather than the long form of vaccines available for 20 million people,” he said.

The public perception is damaging, state and local officials say.

“Had we just projected realistic quantities, the public wouldn’t have seen this as a shortcoming,” said Steven J. Stack, Kentucky’s public health commissioner. “They would have recognized it for the incredible accomplishment it was to even have this much vaccine this fast.”

The foundations of the nation’s vaccine campaign were poured last spring. Since April, key decisions about vaccination planning, budgets and allocation have resided with the leadership of Operation Warp Speed, the public-private partnership set up to accelerate development of coronavirus vaccines and treatments for covid-19, the disease caused by the virus, and to speed their distribution.

Warp Speed’s initial architect, a top Food and Drug Administration vaccines regulator named Peter Marks, envisioned a comprehensive effort that would include extensive federal support to help immunize hundreds of millions of people, with the Centers for Disease Control and Prevention playing a critical role.

Marks left Warp Speed and returned to the FDA in late May, just weeks after the White House publicly announced the effort. And the CDC — the nation’s premier organizer of vaccination drives — wound up taking a back seat as it endured a fraught relationship with Azar and his top aides.

That was a consequential development, said federal health officials who spoke on the condition of anonymity because they were not authorized to speak publicly. Had the CDC played a bigger role, those officials said, forecasts about the number of doses would have been tempered, along with public expectations.

President Trump was vowing to bring in the military, raising concerns among the country’s leading associations of immunization managers and health officials about overturning rather than reinforcing existing systems. In June, they wrote to the leaders of Warp Speed to “strongly recommend building upon existing plans and assessing, enhancing, and utilizing the existing coordinated public and private vaccine delivery infrastructure.”

That same month, Nancy Messonnier, the CDC’s senior official with broad oversight over the vaccination effort, traveled with a colleague from the agency’s headquarters in Atlanta to request approval from Warp Speed and the Department of Health and Human Services for a CDC-led communication and education plan on vaccines, according to one official who spoke on the condition of anonymity to describe internal matters.

“It was general public awareness, to let the public know that vaccines are coming, this is what to expect,” the official said. The CDC “never got the okay to do it.”

Messonnier briefed state health officials in late August on the possibility that two vaccine candidates could soon be available. But the documents and briefing were vague, referring only to “Vaccine A” and “Vaccine B.” One state health official who participated in the call, and who spoke on the condition of anonymity to describe private conservations, said, “We found out from reading in the press which was Pfizer and which was Moderna. They didn’t even tell us that.”

Then, in mid-September, the CDC issued a 57-page interim playbook about coronavirus vaccination, asking states to submit their immunization plans, but with little information about how many doses they could expect or when.

In the interview that day, Saha, vice president of advocacy at Premier Inc., a consultancy that works with about 4,000 hospitals on group purchasing and other health system improvements, said that what was needed was a “federal floor — the minimal standards and baselines that everyone can expect no matter where you go or who you are.”

A week later, in a call with governors, Azar said vaccine was already being stockpiled, even as the products were being tested.

“We anticipate to have manufactured enough vaccine by the end of 2020 to vaccinate our most vulnerable populations,” Azar said at the time.

Vice President Pence described the federal and state partnership necessary to ensure successful vaccination campaigns, asking governors to be ready with plans to administer the shots.

“We need you, number one, to be ready to distribute it and, number two, to do your part to build public confidence,” Pence said, noting that in an election season, he wanted to make sure politics stayed out of the process.

Meanwhile, Trump was demanding that the FDA approve a vaccine before the Nov. 3 election, casting a political shadow over the developments.

HHS and the Office of Management and Budget had redirected money for communications from the CDC to a company in Arlington, Va., for a year-long campaign to “defeat despair and inspire hope” during the pandemic, according to documents provided to congressional committees.

Democrats decried the campaign — which was to feature celebrities friendly to the president — as reelection propaganda. After Azar ordered an internal review, a retooled science-based initiative got underway in December. But the first wave of advertisements designed to boost confidence in vaccines is not scheduled to begin until late January, more than a month after vaccine distribution began.

A federal official involved in planning said skepticism greeted demands in September and October from Warp Speed’s logistics arm that states be prepared to administer vaccine by November, with officials at the CDC and in state government viewing it as election-season posturing. Lingering questions about the potential “militarization of public health” framed those concerns, said the person, who spoke on the condition of anonymity for lack of authorization to address ongoing planning.

One state official recalled a briefing in the weeks leading up to the election with some of the top brass — the FDA commissioner, infectious-disease chief Anthony S. Fauci, the surgeon general and others — that focused almost exclusively on debunking misstatements made by Trump. These officials sought to reassure state leaders that the president would not be able to “make shortcuts to have an election-eve coup,” according to the state official, who spoke on the condition of anonymity to recount internal discussions.

“In retrospect, it’s a bit of a pity, when we could have been discussing logistics and operations, but everyone was really paranoid,” the state official said.

As the election neared, it became more difficult to schedule Azar for updates with state and local health officials. A notice on Oct. 28 from the Association of State and Territorial Health Officials indicated that the health secretary had declined a request for a conversation about funding and other needs.

After the election, Azar had minimal interactions with officials carrying out the vaccination campaign in the states, briefly making remarks at the beginning of calls but engaging very little, according to officials who participated. Gen. Gustave F. Perna, chief operating officer of Operation Warp Speed, had one-on-one calls with state officials, most often governors, in addition to group briefings. He was generous, often giving out his personal cellphone number, but not prepared to discuss the ground-level challenges of immunization, said multiple state health officials who have spoken with him.

Azar contested the portrayal that he has not communicated with health officials, saying he participates nearly every Monday afternoon in a virtual meeting Pence convenes with governors, some of whom invite their health departments to attend. “Their state [health] officials are available on video or telephone on these calls,” Azar said. “When I’m looking up at the video, they are sitting right there on the call.”

The last time officials in San Antonio — one of six metro areas considered its own jurisdiction for federal vaccine planning — spoke to Perna was Dec. 3, said Colleen Bridger, the city’s interim health director.

Federal officials maintained that Perna and others have been immediately available to local authorities, with one senior administration official saying the four-star Army general recently spoke to 15 governors on a single day.

“The problem was that, over the holidays, those communications fell off, and then there were a lot of decisions made that were different from what our regular calls had communicated,” Bridger said.

The December launch dates of the two vaccines created immediate headaches.

State officials worked through Christmas and into the new year, dealing with the daunting logistics of administering limited supplies of shots that, in the case of the Pfizer vaccine, come in 975-dose batches.

“My wife asked, ‘Why are you on a conference call at 8 o’clock on New Year’s Eve?’ ” said Randall W. Williams, Missouri’s health director.

Scheduling vaccinations at nursing homes and assisted-living centers was challenging — the responsibility of CVS and Walgreens, which operate influenza vaccination clinics.

“In some cases, we have had to make 10 to 12 phone calls’’ to lock down a schedule for a visit, said Larry J. Merlo, chief executive of CVS Health.

Part of the reason for slow uptake has been hesitancy among staff members, with only about 30 to 40 percent willing to get shots, according to officials and executives.

April Verrett, president of the Service Employees International Union Local 2015, which represents long-term care workers in California, said the federal government, nursing homes and chain pharmacies did not offer education programs for workers.

“I just think the plan is not very well thought out,’’ Verrett said.

The week of Christmas was especially chaotic, as states acted on their own, abruptly expanding eligibility to millions of people.

In some states, those changes sparked tensions among local and state officials.

In Florida, Gov. Ron DeSantis (R) declared that the state’s older residents would follow front-line medical workers in gaining access to vaccines. He acted without consulting state health officials stationed in Florida’s 67 counties, according to a health official who spoke on the condition of anonymity because of a lack of authorization to address the matter publicly. Some counties had plans in place to immunize emergency workers so they could administer shots to others — an arrangement that was jettisoned as thousands of elderly residents suddenly clamored for the vaccinations.

In Texas, a directive instructing providers not to wait to complete one priority group before moving to the next led health authorities in San Antonio to overhaul their plan.

“So now all of a sudden we’re in a mass vaccination model, but remember public health has been staffing the pandemic since early 2020, and so we have a workforce that’s really tired,” Bridger said.

Hospital executives also highlighted as cumbersome the prioritization tiers for vaccine imposed by different states, with large numbers of employees not responding to emails inviting them to get vaccinated and others opting to wait until after the holidays.

Some hospitals began turning to volunteers.

At Tucson Medical Center in Arizona, one of the states hit hardest by the winter coronavirus surge, the hospital set up a drive-through system staffed in part by dozens of volunteers.

“We are in a disaster staffing plan and have been now for several weeks,’’ said Judy Rich, chief executive of Tucson Medical Center.

Only in the economic stimulus package lawmakers passed at the end of the year did funding come through for the states, which for months had pleaded with the administration and Congress for about $8 billion to train additional vaccinators, improve data systems and do outreach to priority populations.

Pennsylvania officials said the delay left them unable to launch public education campaigns on radio, television or digital media, or billboards and bus signs, or even print basic educational materials.

“We need a Smokey Bear or an anti-smoking-type campaign,” said Patricia A. Stinchfield, a nurse practitioner and immunization expert at Children’s Minnesota, who lamented the lack of coordination among institutions, each of which developed its own scheduling plan, putting enormous strain on information technology departments. She warned that the organizational challenges will grow as more people become eligible for vaccines.

The path ahead remains unclear.

Sen. Patty Murray (Wash.), the ranking Democrat and soon-to-be chairman of the Senate Committee on Health, Education, Labor and Pensions, described a conversation last week with Perna.

“What I heard from him is that it’s up to states,” said Murray, who released a white paper in July addressing the need to ensure an adequate workforce and set up sites to administer vaccines. “His position was, ‘They’ve got plans.’ ”

On Thursday, the American Hospital Association, which represents 5,000 hospitals, and other health-care organizations sent a letter to Azar urging stronger federal leadership, coordination and accountability.

Richard J. Pollack, the association’s chief executive, said shortages of critical supplies are already occurring. “It’s those kinds of things where we need a mechanism to send up those flares and get them addressed in a very quick way,” he said.

Only last week, after criticism about the slow rollout, did the federal government give states the option of accelerating chain pharmacies’ involvement in the immunization effort. Pharmacy leaders had been telling Operation Warp Speed for weeks that they were equipped to play a bigger role sooner than planned.

The pharmacy plan was developed by the CDC, and the decision to “turn it on” early was made last week at Camp David, Md., where Azar met for three to four hours with federal health officials and Warp Speed leaders to discuss plans for vaccines and therapeutics in the last days of the Trump administration. Participants included Perna and Moncef Slaoui, Warp Speed’s chief science adviser.

CDC officials were not included.

Meanwhile, disagreements among Trump administration officials have flared. Some top health officials were taken aback when Slaoui appeared on TV suggesting that the FDA was discussing with Moderna possibly cutting doses in half to provide more vaccine to more people, faster.

“Slaoui was shooting from the hip,” said a senior administration official who spoke on the condition of anonymity for lack of authorization to talk publicly about the issue. The FDA said last week that it was not considering reducing Moderna’s doses because there wasn’t adequate data to support such a move.

President-elect Joe Biden on Friday signaled the first change he intends to make in the nation’s vaccination campaign: stopping the Trump administration’s practice of withholding about half of the available doses to ensure enough are available for the required second shots. The incoming administration has said it will elaborate on its vaccine strategy this week.

Francis S. Collins, director of the National Institutes of Health, said in a Washington Post Live interview Wednesday that he expects the pace of vaccinations to pick up soon and warned against “tinkering with the timing of the doses” or going “outside of the scientific data.”

“Let’s all be a little patient and not conclude that we’ve got a major challenge that’s been not met yet until we have a little bit more time to see how it goes,” Collins said, adding that in weekly calls among governors, states were learning from one another as they face immunizing 80 to 85 percent of the population in hope of achieving herd immunity by June or July. He predicted that the nation is headed toward delivering 1 million injections a day.

Still, the turmoil disturbs experts such as Kelly L. Moore of the Immunization Action Coalition, who directed Tennessee’s immunization program during the H1N1 flu pandemic in 2009 when she helped create a statewide vaccination system.

“I just wish we could come together and agree on a coordinated effort nationwide,” Moore said. “There’s a lot of wisdom that could have helped us think through these situations before they arise.”