A largely unmasked nation will celebrate the nation’s return to near-normalcy this weekend with a ticker-tape parade in New York City, a dazzling fireworks display over the Washington Monument and countless Independence Day gatherings in cities and towns across the country.

“A summer of freedom. A summer of joy,” is how the White House tried to promote a new national mood in a letter encouraging local officials to hold public events during the July 4th holiday.

And in most parts of the country, Americans have reason to cheer, with more than half of those over 12 fully vaccinated, state after state lifting all emergency restrictions and caseloads decreasing by double-digits week over week. Families are traveling again, diners are flocking to restaurants and baseball is back as America’s seasonal pastime.

But the summer is turning out to be fairly joyless in places like CoxHealth Medical Center in Springfield, Mo., where nurses, doctors and respiratory therapists have been grappling with a resurgence in coronavirus cases that forced the hospital to reopen the 80-bed Covid unit it had shuttered in May.

Dr. Terrence Coulter, a critical care specialist at CoxHealth, said he and his colleagues were stunned to find themselves back in the trenches after the briefest of respites. “With everyone masked, you learn to read the emotions in your co-workers’ eyes,” he said. “They’re weary and they’re also disappointed that the country has started the end zone dance before we cross the goal line. The truth is we’re fumbling the ball before we even get there.”

America’s health care workers are in crisis, even in places that have had sharp declines in coronavirus infections and deaths. Battered and burned out, they feel unappreciated by a nation that lionized them as Covid heroes but often scoffed at mask mandates and refused to follow social distancing guidelines. Many of those same Americans are now ignoring their pleas to get vaccinated.

Doctors and nurses are also overworked, thanks to chronic staffing shortages made worse by a pandemic that drove thousands from the field. Many are struggling with depression and post-traumatic stress; others are mourning at least 3,600 colleagues who won’t be around for the celebrations.

“People don’t realize what it was like to be on the front lines and risking your own safety without adequate protective gear while dealing with so much death,” said Mary Turner, a registered nurse in Minneapolis who was unable to comfort her own father as he lay dying alone of Covid in a nursing home in the early days of the pandemic. A few months later, she found herself sobbing uncontrollably in a hospital room as she held up a phone so a man could say goodbye to his father. “A lot of us are still dealing with PTSD,” she said.

In recent weeks, a familiar sense of dread has returned to emergency rooms across the South and Mountain West as the more transmissible Delta variant gained traction among the unvaccinated, fueling a jump in hospitalizations. In Missouri alone, caseloads increased more than 40 percent from two weeks earlier; at CoxHealth where Dr. Coulter works, the Delta variant comprised 93 percent of all cases last week, he said.

Dr. Clay Smith, an emergency room doctor who travels between two distant hospitals in South Dakota and Wyoming, said he worried about his children, who are both too young to get inoculated. “It’s really disconcerting to work in a community where people are doing so little to protect themselves and others from the virus,” Dr. Smith said.

With fewer than a third of adults in the counties served by the hospitals fully vaccinated, he has been treating a small but steady stream of Covid patients, some of whom insist the coronavirus is a hoax even as they struggle to breathe. “People think they are exercising their rights by refusing to get vaccinated, but in reality they’re exposing themselves and others to risk,” Dr. Smith said.

Some health care workers are also refusing to get jabbed. Last month, 153 employees at the Houston Methodist hospital system resigned or were terminated after they refused to abide by a policy requiring all staff to be vaccinated against Covid. Similar standoffs over vaccine mandates will most likely multiply as hospitals across the country embrace similar policies.

In interviews, nearly two dozen health care providers expressed a range of conflicting emotions: Elation over how quickly the vaccines were created and relief that the pandemic’s darkest days are in the past, but fear that the large number of unvaccinated Americans could lead to localized outbreaks that persist for the foreseeable future.

Few are in a celebratory mood.

Deborah Burger, co-president of National Nurses United, a union that represents 170,000 registered nurses, said the revelries planned for the Fourth of July weekend felt ill-conceived and tone deaf, and not just because the pandemic continues to claim hundreds of lives a day.

Nurses, she said, face a welter of indignities at work. Dire staff shortages are preventing many from taking much-needed vacations, and some hospitals are still requiring employees to reuse disposable N95 masks even though supply chain bottlenecks have eased. Then there is the open hostility from patients who have spent months steeped in right-wing commentary and conspiracy theories that have turned health workers into adversaries.

“I’ve been in the field for 45 years and I’ve never seen things this bad,” said Ms. Burger, who is a registered nurse. “It’s really frustrating and dispiriting that the pandemic has been turned into a political event, rather than a public health crisis, and it’s health care workers who are left to deal with the aftermath.”

The pandemic continues to vex hospitals and their employees, often in unexpected ways. Dr. Mara Windsor, an emergency room doctor in Phoenix, rarely sees Covid patients these days, but she said an alarming shortage of nurses had gummed up the admissions process, forcing patients to wait upward of eight hours before they can be seen by a doctor. The problem is shared by hospitals across the city.

Infuriated patients, she said, often scream at her; others will storm out before they can be treated. “It’s very anxiety provoking to have 30 patients in the lobby and not being able to take them because we have no nurses,” said Dr. Windsor, who has been forced to scale back her hours and take a pay cut because of the drop off in admissions. “What if someone has a heart attack? The whole environment has become really challenging.”

The conflict over vaccines has complicated, and sometimes curdled, the relationship between patients and health care providers. As a woman of color well aware of the systemic racism in American health care, Dr. Mati Hlatshwayo Davis, an infectious disease doctor in St. Louis, said she was sympathetic to the vaccine-hesitant but that she sometimes struggled to contain her frustration, especially given that her sisters in South Africa had little hope of getting the shots any time soon.

“There are moments of overwhelming joy when seeing patients I know who survived Covid, but then I’ll treat multiple members of a family with Covid or we will have to intubate someone and you can’t help but think this was preventable,” she said. “It’s heartbreaking, but we’re also really, really tired.”

Dr. Teena Chopra, the medical director of infection prevention and hospital epidemiology at the Detroit Medical Center, takes a no-nonsense approach with the Covid patients she treats, most of them increasingly young. Although caseloads across the state have dropped significantly since a calamitous third surge ended in April, only 51 percent of adults in Michigan have received one vaccine dose. In Detroit, that figure is 40 percent.

The interactions she has with Covid patients, many of them African American, often leave her shaken. She recalled a recent exchange with a woman in her 40s who was struggling to breathe. When Dr. Chopra asked whether she had been vaccinated, the woman shook her head defiantly between gasps, insisting that the vaccines were more harmful than the virus. The patient later died.

“It leaves me angry, frustrated and sad,” Dr. Chopra said. “These nonbelievers will never accept our viewpoint, and the result is that they are putting others at risk and overwhelming the health care system.”

The emotional fallout of the last 16 months takes many forms, including a spate of early retirements and suicides among health care providers. Dr. Mark Rosenberg, an emergency room doctor at St. Joseph’s University Medical Center in Paterson, N.J., a predominantly working class, immigrant community that was hit hard by the pandemic, sees the toll all around him.

He recently found himself comforting a fellow doctor who blamed himself for infecting his in-laws. They died four days apart. “He just can’t get past the guilt,” Dr. Rosenberg said.

At a graduation party for the hospital’s residents two weeks ago — the emergency department’s first social gathering in nearly two years — the DJ read the room and decided not to play any music, Dr. Rosenberg said. “People in my department usually love to dance but everyone just wanted to talk, catch up and get a hug.”

Dr. Rosenberg, who is also president of the American College of Emergency Physicians, is processing his own losses. They include his friend, Dr. Lorna Breen, who took her own life in the first months of the pandemic and whose death has inspired federal legislation that seeks to address suicide and burnout among health care professionals.

Most of the suffering goes unseen or unacknowledged. Dr. Rosenberg compared the hidden trauma to what his father, a World War II veteran, experienced after the hostilities ended.

“My dad didn’t like to talk about the war but once in a while he did and what he said was that so many of his fellow soldiers died after they came home,” he said. “We would now describe this as PTSD, and I see the same thing happening among health care workers.”

Dr. Rosenberg said he had mixed feelings about the festivities planned for July 4. He is proud of the camaraderie and self-sacrifice he witnessed among colleagues who bravely faced down a deadly virus, but he is uncomfortable with the expression “health care heroes,” especially given the widespread resistance to vaccinations.

“We’re ready to stand shoulder to shoulder again and face whatever comes our way,” he said. “But to be honest, we’re wiped out and we just want society to show us that we really are appreciated — by getting vaccinated.”