Among the many difficulties imposed upon America by the pandemic, the scourge of anti-vaccine sentiment—and the preventable deaths caused as result—ranks among the most frustrating, especially for infectious-disease doctors like me.

People who are hospitalized with COVID-19 rarely refuse therapy, but acceptance of vaccines to help prevent infection has been considerably more limited. Seventy percent of Americans have received the initial complement of vaccine injections, and many fewer have received the boosters designed to address viral variants and confer additional protection. Why are so many people resistant to this potentially lifesaving treatment?  

Some explanations are unique to our era—the awful weaponization of science in a deeply partisan political environment during the age of social media, for instance. But the concept of vaccine hesitancy is not new. Such hesitancy is, in a larger sense, a rejection of science—a phenomenon that far predates the existence of vaccines.

One of the earliest documented controversies in science denialism comes from the field of astronomy. In the third century B.C., the Greek astronomer Aristarchus of Samos proposed a heliocentric model of the universe. The idea that the Earth and planets might revolve around the sun, rather than the other way around, was shocking at the time, and Aristarchus’s theory was quickly rejected in favor of models such as those put forth by Aristotle and Ptolemy, both of whom insisted that the Earth was the center of the universe. The fact that Aristotle and Ptolemy remain better known today than Aristarchus shows the force of the rejection. It would be some 2,000 years before the notion was seriously reconsidered.   

In the 1530s, the Polish astronomer Nicolaus Copernicus developed his own heliocentric model based on astronomical observations. Copernicus is remembered today primarily for this perspective-changing discovery. But it’s worth noting that he delayed publication of his findings until 1543, the year of his death, perhaps for fear of scorn or religious objections.  

In the early 17th century, Galileo Galilei, the Italian astronomer known as the “father of modern astronomy,” recognized that explaining the celestial changes in the position of stars and sun over time required that the Earth revolve around the sun. Galileo fully and publicly supported the Copernican theory of a heliocentric universe, and condemnation from the Vatican was swift and harsh. He was tried by the Inquisition and threatened with excommunication if he did not recant. Rather than incur the wrath of the pope, he finally agreed that he was wrong. He spent the remainder of his life under house arrest. It would be another 180 years before the Church admitted that Galileo was right.

Rejections of scientific advances are found throughout the history of medicine. There have been four great advances in medicine over the past 200 years: anesthesia, antisepsis, antibiotics, and immunization. Not every advance was met with resistance. When the benefits of the advance have been obvious, there has tended to be little hesitation. Anesthesia and its cousin, analgesia, for instance, were rapidly accepted; they relieved pain, and the advantages were readily appreciated.  

Antisepsis had a stormier path to public acceptance. In the 19th century, English and Irish physicians recognized that puerperal sepsis (a dangerous infection in a mother after delivery of a baby) was likely a contagious condition that was spread from patient to patient either by the medical staff or the local environment. They suggested that improving hygiene would reduce the high rates of mortality that puerperal sepsis caused. In 1843, Oliver Wendell Holmes Sr., a physician (and one of The Atlantic’s founders), presented a paper to the Boston Society for Medical Improvement titled “The Contagiousness of Puerperal Fever.” Holmes suggested that unwashed hands among the medical and nursing staff were responsible for transmitting puerperal fever. This did not sit well with the establishment. A prestigious Philadelphia obstetrician, Charles D. Meigs, declared Holmes’s findings to be nonsense and suggested that an increased number of cases among any physician was just bad luck.  

The physician who is most frequently recognized with establishing the contagious nature of this infection is a Hungarian obstetrician, Ignaz Semmelweis.  He noted that patients in the Vienna General Hospital who were cared for by physicians had a higher incidence of postpartum sepsis than those who were cared for by midwives. Semmelweis realized that physicians performed autopsies, whereas midwives did not, and that physicians did not wash their hands or clothing before moving from an autopsy to a delivery. (It was routine for them to attend deliveries in their bloodstained clothing, having come directly from the autopsy suite.) When he suggested simple hygiene measures such as handwashing, he was derided and eventually run out of town. The medical establishment was unwilling to accept that physicians—rather than bad air or host weaknesses—were responsible for spreading infections and harming patients.

Science denialism can work in the other direction too. When antibiotics, especially penicillin, were first introduced, they were rightly appreciated as miracle drugs. In the pre-antibiotic era, the leading cause of death among children was infectious diseases. The use of antibiotics was astoundingly successful against many, but not all, childhood diseases. The downside for this enthusiasm for treatment came when patients demanded antibiotics for conditions—such as viruses—that didn’t actually necessitate them. Fifty years ago, telling a patient that they had a virus and that penicillin was therefore of no use led to disappointment, disbelief, and even arguments from patients requesting antibiotics for simple colds. Many doctors gave in because it was simpler than spending time fighting with a patient. A consequence of the more indiscriminate use of antibiotics—which represents its own mini-genre of science denialism—has been increased bacterial resistance.

But of the four great advances, none has so broadly helped humanity, or suffered more from science denialism, than immunization. Most, but not all, of the vaccines that scientists have developed since the first immunizations in the 18th century have been developed against viruses. Of all viral infections, the most feared may well have been smallpox. Over the course of the 20th century alone, an estimated 300 million people died of smallpox. Smallpox is highly contagious and spares no age group or class. Its common form has an estimated overall mortality of roughly 30 percent, but the mortality of hemorrhagic smallpox—a more severe form of the disease—approaches 100 percent. Smallpox is also wildly contagious, a characteristic that is most evident when a previously unexposed population is exposed. Smallpox was unknown in the Americas before European explorers brought cases to the New World. The disease decimated the Indigenous populations of North America and South America as a result.

The early concept of immunization to prevent smallpox may have begun more than 1,000 years ago, in China. The history is contested, but some documents show that children would be made to inhale material from a ground-up, mature smallpox lesion scraped off of the body of the infected—a level of exposure that could trigger a person’s immune response to smallpox without causing a full-blown infection. A later technique, which involved scratching the skin of an uninfected individual with material from another person’s lesion, was observed by the wife of the English ambassador to Istanbul, who then brought this procedure to Europe. She was so impressed that she had her children immunized. Subsequently, an experiment was done in which six prisoners in London were immunized. Despite exposure to smallpox, none of them became ill.

Like many advances in medicine, smallpox immunization was met with some resistance, including worry that immunization might inadvertently spread the disease to others. This was an understandable reaction; the live smallpox virus was used, and a small percentage of inoculated individuals did develop full-blown disease and die. In 1721, there was an outbreak of smallpox in Boston. The writer and clergyman Cotton Mather urged widespread immunization but had only moderate success because of resistance from the local population.  (History complicates even the views of those who embrace science: Mather was also an ardent defender of the Salem witch trials.) Years later, a well-known case of immunization resistance occurred in Philadelphia. During an outbreak of smallpox in 1736, Benjamin Franklin’s 4-year-old son, Francis, became infected and died. Francis had not been immunized despite an opportunity to do so, and Franklin said he regretted the decision for the rest of his life.   

In the generations that followed, scientists built off of these earlier methods and eventually developed a stable and widely available smallpox vaccine. The global eradication of smallpox as a result remains one of the greatest accomplishments in the history of medicine. The last case of naturally occurring smallpox was reported more than 40 years ago.

Even so, vaccine hesitancy has persisted. In America, new vaccines for other diseases have continued to prompt their own waves of skepticism and hostility. And although science denialism is not pervasive in the way it once was centuries ago, it still rears its ugly head. The arrival of the COVID-19 vaccines brought pernicious vaccine sentiments into the spotlight. The reasons for this vehemence are many. For instance, some people who might accept the efficacy of a vaccine have such a fear of injections that they simply avoid seeking medical care until absolutely necessary. But this represents a minority of those who reject the vaccines.

A more common—and more insidious—force that pushes people away from lifesaving vaccines appears to be swelling distrust in expertise, which is both a political and cultural phenomenon. Vaccine resistance can be peddled by influential people in both liberal and conservative circles, but throughout the pandemic, right-wing anti-government organizations and television personalities in particular have promoted a stew of outrageous conspiracy theories about vaccines. Run-of-the-mill misinformation remains a problem too. Some people continue to believe that the COVID-19 vaccine will infect you and make you sick—this is not the case. Finally, of course, there are concerns about known and unknown side effects from the vaccination. Like many vaccines, the COVID shots are linked to serious health effects in extremely rare circumstances; for instance, Moderna’s and Pfizer’s mRNA shots are associated with a very small risk of heart inflammation. It is virtually impossible to prove that some side effect will not ever occur. But hundreds of millions of people have safely received the COVID vaccine in the United States alone.  

Perhaps the greatest disservice to vaccination has been the fraudulent claim that childhood vaccines cause autism. This claim was originally published in an otherwise respected medical journal in the 1990s, and has since been fully retracted. (The author lost his medical license.) Nevertheless, many people still believe this and have put their children at risk for serious illness as a result.

Our advances in science over the past two centuries have truly been extraordinary, but our society still suffers from the forces that reject reason and prevent our ability to take full advantage of discoveries that protect us all. And we need to push back against those who endanger others because they see opportunities for fame or profit in spreading dangerous disinformation. Until that happens, our species will continue to understand the world around us in fits and starts—with too many people dying, even when we know how to save them.

An unusual animal with canine teeth similar to those of a saber-toothed cat and the wide-set eyes of a cow lived in South America some 5 million years ago.

A supplier is under investigation after pre-packed meat was found to be from South America and Europe.

Police reveal details of an undercover operation that began off the coast of South America.

Rock Creek Park was still dark when the killer emerged from his den, a flame-colored phantom on black-stocking legs. With exquisite night vision, the fox surveyed the contours of the park’s forests and the curves in its stream. At the woodland’s edge, he could see the glow of Washington, D.C. He pressed his paws into exposed soil, indenting it with diamond-shaped prints that grew farther apart as he accelerated into a trot.

That it was early May indicates that the fox was likely a new father, a detail that has gone unmentioned in published accounts of his crime. The cold months are cuffing season for foxes. After mating, pairs move in together to raise kits, usually by expanding a burrow abandoned by a woodchuck or skunk. In springtime, the hills of Rock Creek Park are alive with these renovated dens. When litters are born, in late March or early April, the kits remain in their depths for nine days, curled up nose to tail, eyes closed serenely. Only recently had the park’s kits ventured toward the mouths of their little caves, to flop around with their siblings and play tug-of-war with bones while awaiting their fathers’ return from the hunt.

It’s not clear whether the fox had his final destination in mind as he moved through dense stands of sugar maples, oaks, and beeches under the light of a crescent moon. With his swiveling ears, he would have heard cars whooshing down nearby streets. This noise had quieted during the pandemic, when D.C.’s mayor closed restaurants and human life drained out of downtown. But by last May, the city was again thrumming with traffic, increasing the appeal of hunting targets within the park, especially its ultimate garden of forbidden treats: the Smithsonian National Zoo.

Spread across the zoo’s grounds are more than 100 enclosures where bamboo-bingeing pandas, neon tree frogs, and all manner of other creatures are held for the viewing pleasure of visitors. These enclosures have been refreshed since the zoo opened in 1891: Steel bars have been replaced with moats, stone walls, and other naturalistic barriers to deemphasize the aesthetics of the cage. Changes like these have proved soothing for visitors, but the animals remain confined in spaces that constitute a tiny fraction of their natural range.

Senior staff at the zoo told me that they try to respect the layered local ecology, which includes the larger park and the surrounding concrete expanse of the capital. The zoo’s perimeter fence may be 8 feet tall and topped by barbed wire, but that’s mainly to keep people out at night. “Guests do stupid stuff,” one staffer told me. “If you’re not careful, someone will come in and smack an elephant on the rear end and run.” Otherwise, the borders between the forest and zoo are as porous as possible, so as not to interrupt the wildlife corridors that crisscross D.C. like Metro lines.

If officers from the zoo’s dedicated federal law-enforcement agency spot a white-tailed deer on a control-room monitor, they do not express alarm. Raccoons that fish ice cream from the trash are likewise tolerated. One curator told me that juvenile bears have recently been spotted in Rock Creek Park and that she wouldn’t be surprised if she soon sees one strolling down the zoo’s central path. Even foxes are welcome to roam the grounds, subject to certain limitations, which are strictly enforced: If, for instance, a fox indulges his darker vulpine impulses and hunts the zoo’s animals, he will swiftly be brought to justice.

The fox seems to have entered the zoo by slinking up a wooded hillside on its southern edge, his white-tipped tail bobbing behind him like a wind sock. We don’t know exactly what lured him to the level path that runs along the back of the Bird House, although given that he hails from a multimillion-year hunting tradition, it may have been his well-honed sense for easy prey.

During the 20th century, most zoo animals were plucked roughly from biomes across the planet until eventually a distaste for these abductions settled in among the public. In accredited zoos today, most are bred from existing captives. Breeding arrangements span a global network of zoos, but gene pools remain limited, making some of the animals vulnerable to genetic disease. Life in captivity can also diminish animals’ immune system, not to mention their morale. The fox may have made previous visits to the zoo and noticed that its captives don’t always move with a wild animal’s sense of purpose and alertness; some may have been in outright distress. He may have wandered just beyond the Bird House to the sloth-bear enclosure, where the bears have been seen pacing in circles, a behavior also exhibited by this zoo’s tigers, and many other large captive mammals across the world.

An old Rilke poem describes the pacing of a caged animal as a ritual dance of “powerful soft strides … around a center / in which a mighty will stands paralyzed.” Depression is the word we use to describe a paralysis of will, and captivity inflicts a special form of it on animals, which we call “zoochosis.” Those suffering from it sometimes pluck their own fur compulsively, and may even mutilate themselves. These are obvious signs that something is amiss with an animal, but a fox may be attuned to others that are less legible to us.

At the back of Bird House, the fox may have noted the way the 74 flamingos ambled across their nearly 10,000-square-foot enclosure. Something about their movements may have struck him as curious. Great hunters of birds, foxes have cognitive processes that may contain an algorithm alerting them when an animal’s wings aren’t working. In the wild, some flamingos power up to Andean peaks or glide, pelicanlike, for miles along the coast. But not these flamingos. They were permanently grounded when zoo staffers removed their flight feathers three days after they were born, to make sure they wouldn’t escape their enclosure.

Wing clipping is cruel in part because it shrinks a bird’s world: A land animal’s range is a two-dimensional shape on a map, but a flying being can explore a truly voluminous chunk of the Earth’s atmosphere. Grounded birds are also more vulnerable to mass slaughter. If a fox came upon a flamingo flock in the wild, he’d be lucky to get his teeth into one before the rest flew away. But the zoo’s flamingos would never fly away, even under direct attack. They couldn’t. They were trapped like hens in a coop.

Jim Naughten for The Atlantic

The fox had to work to get into the Bird House. As a rich target, it’s well fortified. “It has the right-size animals for the predators we have,” Bill McShea, a wildlife ecologist at the zoo, told me. When the zoo’s American flamingo exhibit first went on outdoor display in the 1970s, the birds were surrounded by a fence that, for more than 40 years afterward, kept them successfully protected. Six years ago, it was replaced with a fence made of stainless-steel mesh that met national enclosure standards, which change to keep pace with the ever-evolving creativity of animals. Every day since, the new fence had been checked, most recently at 2:30 the afternoon before the fox arrived, when it was found intact.

Tales of fox cunning are as old as culture. Aesop’s foxes were constantly involved in deceptions. In Apache lore, a thieving fox stands in for Prometheus, stealing fire for humans. I imagine that at the zoo, the fox walked back and forth along the flamingo fence, sussing out its vulnerabilities. Tunneling underneath wasn’t practical: A concrete dig barrier extends underground, too deep for a single night’s digging. If the fox tried to chip away at it over several nights, zookeepers would have noticed. Whether out of insight or frustration, at some point in the dark hours before dawn, the fox began to grind the fence mesh between his teeth. Like a spy cutting a circle of glass out of a high-rise windowpane, he was able to chew a softball-size hole in the fence and, with some wriggling, slip through.

Flamingos are large birds; some weigh nearly half of an adult male fox. Their size did not deter him. “Foxes are the ultimate opportunists,” Dan Rauch, a wildlife biologist for D.C., told me. “They’re happy to make meals of field mice, snakes, Canada geese, and everything in between.” Keeping low to the ground, the fox would have moved toward the birds in quick, measured steps. If he saw one of the birds glance in his direction, he would have stilled every muscle. When he got within leaping range, an adrenal thrill would have surged through his limbs. Feeling playful, like a kit romping around in the den again, he would have sprung forward in a lethal pounce.

Sara Hallager arrived at the Bird House just after 6 o’clock that morning. As the zoo’s head curator for birds, Hallager makes sure to check on the animals first thing when she works the early shift, methodically looking in on the cranes and herons. When she reached the flamingo enclosure, she was alarmed to find herself eye to eye with the fox. Not all foxes react skittishly upon spotting a human, but this one seemed to have consciousness of guilt. “As soon as he saw me, he ran away through the hole in the fence that he had created,” Hallager told me. Any hopes that the fox had just arrived were dashed when she saw that pink-feathered mayhem was strewn across the enclosure’s bare soil and in its shallow pool. “I could already see a large number of dead flamingos,” Hallager said.

Hallager is one of the National Zoo’s longest-serving curators. She started as a volunteer in 1984, helping hand-rear tiger cubs, baby seals, and red pandas. She met her husband, another lifer, at the zoo. Today, she oversees a team of 10 curators and keepers who care for more than 400 birds, including gem-colored hummingbirds and ostrich-size rheas. For the past six years, she helped lead a $69 million renovation of the Bird House, along with a major shift in its curatorial philosophy. No longer will the zoo acquire birds from Africa, Asia, or South America, she told me when I visited her there earlier this winter. Instead, new exhibits will showcase North American birds. The idea is to tell a story about protecting the wildness of this continent against the backdrop of Rock Creek Park. A long-standing migratory way station, the park’s forests sit on the Atlantic flyway, a coastal path traveled annually by millions of birds, which together make up an airborne river of song that runs all the way up to the Arctic.

Instead of putting the final touches on one of her new exhibits, that morning Hallager found herself presiding over a grisly scene. She called two keepers who were already on-site at a different part of the zoo, and they immediately ran over to help. The zoo’s vets arrived about 30 minutes later. They have a special van for ferrying animals up to the on-site hospital, where an open bay feeds into a pair of operating rooms. On the rare occasion that a lion requires surgery, zoo protocol insists on a special police escort, but no police were needed to move the flamingos. “We tried to triage the birds that were obviously injured,” Hallager told me. They were able to save three but lost 25 others—more than a third of the flock—plus a pintail duck. The victim tally made for shocking headlines, but it had a simple explanation: Foxes operate on a “kill now, eat later” philosophy. When Hallager happened upon the fox, post-rampage, he’d already buried two flamingos in the sand, beak to toe.

The flamingos are managed as a group, which means they aren’t given individual names, except for those raised as chicks by keepers. Hallager had dribbled baby-bird formula into some of the flamingos’ tiny beaks and watched as they grew into adults capable of living into their 50s. She described them to me as “charismatic, cranky, and very funny.” Zoo leaders made grief counselors available to her and the other keepers, just as they had when two elephants died of old age during the pandemic. She described the elephants’ deaths as profound experiences for the staff, but the loss of the flamingos just struck her as tragic. “The pictures I have in my mind from that morning haunt me to this day,” she said.

Last month, I met with Bryan Amaral, who runs animal care for the entire zoo, to discuss the institution’s response to “the flamingo incident,” as he called it. Over coffee in a large conference room not far from the cheetah enclosure, he told me that he has had to deal with a range of animal intruders over the course of his career, including a Florida alligator that snuck into Disney’s Animal Kingdom and bit an elephant. In the case of the fox, “we didn’t have the attack on film,” he said. “All we could do was CSI the situation to the best of our ability.”

Foxes have hunted captive flamingos in bulk before. In 1996, one snuck past the red-coated guards at Buckingham Palace and killed six flamingoes that Queen Elizabeth II kept as garden pets. In 2014, another fox broke into Germany’s Frankfurt Zoo and killed 15 flamingos. Some of the birds were granted a dignified death: A single bite snapped the pink velvet rope of their neck. Others were fully decapitated.

When caught committing these acts of ultraviolence, foxes can be first-rate escape artists. In ranching country, they’ll run through herds of sheep to break up their scent trails. In snow, they’ll wave their floofy tails back and forth, possibly to broom away their tracks. No one at the zoo tried to pursue the fox after he dashed away from Hallager, but the staff worried that he’d strike again. Like many killers, he might not be able to resist returning to the scene of his crime, especially if he had hungry kits awaiting flamingo meat back home. What if next time he killed a whooping crane, or one of the zoo’s other endangered birds?

Keepers set about bolstering the fence surrounding the Bird House. They also set cage traps around the perimeter of the flamingo exhibit. Amaral told me that he holds no grudge against foxes in general. “We didn’t want to indiscriminately trap foxes around the zoo,” he said. “We tried our best to target the perpetrator.” More than a week later, they found a frantic fox rattling around in one of the traps, but they’re not sure that they actually nabbed the actual culprit. During my conversation with Hallager, she made sure to emphasize that they’d caught a fox, not necessarily the fox.

Amaral explained that a DNA test had proved inconclusive, and that a police lineup was obviously impossible. Despite this uncertainty, the zoo’s staff immediately initiated Phase 2 of their plan: A plastic bag was draped over the cage trap, shrouding the fox in a dark balloon. Anesthetic gas was pumped in until he fell asleep. After he was sedated, a syringe dripping with barbiturates was pushed into his orange fur until it punctured his skin like a venom-filled fang. Inside the rib cage of every fox is a small but mighty heart that beats up to 400 times a minute when the animal is trying to escape death. His stopped within minutes.

I asked Amaral whether there was any internal dissent about killing the fox. He told me that no one had lodged any objections, so far as he could recall. This unanimity among the staff surprised me. It struck me as contrary to the zoo’s spirit. At the very least, it seemed like a failure of imagination. Surely an institution devoted to caring for animals should have found a way to spare the fox. Why not relocate him to a forest across the Anacostia River?

“That would lead to all kinds of issues,” Amaral said. Apart from humans, red foxes have the most extensive natural range of any land mammal on the planet. They’re at home in North Africa’s deserts, in the Taiga, in the mountains of Argentina, and in the Canadian Arctic. In the United States, their distribution is dense because European settlers killed off cougars and red wolves, their natural predators. Anywhere the fox was relocated, Amaral argued, he’d soon find himself in a deadly turf war. “It would be like remote euthanasia,” he said.

I left the zoo unsettled. I couldn’t shake the sense that the fox had been wronged. The very next night, I experienced a visitation. In the predawn hours, I awoke to a sudden, high-pitched scream. For 30 seconds, I laid still in bed, thinking that the sound was a remnant of an unremembered dream. When I heard it again, I leapt up to my window and swept the curtains aside. To my astonishment, a fox was sitting on the sidewalk directly in front of my house, screeching into the dark wintry air, trying desperately to summon a mate. This went on for several minutes until headlights beamed down the street and he fled.

Later that week, during some late-night Googling, I learned that several zoos in the eastern United States exhibit red foxes, presumably to showcase one of North America’s most vivid manifestations of wildness. Two of the zoos were in Florida, in Melbourne and Naples. Another was in Little Rock, Arkansas. I emailed Amaral to ask if he’d considered moving the trapped fox to a different zoo. He wrote back to say no, on account of all the preplanning it would have required. Among other complexities, the zoo would have had to care for the fox during a lengthy quarantine. “We were acting quickly in response to a crisis with a known skilled predator,” he said. Fair enough, I thought. Perhaps it’s just as well. Confinement is no life for an animal, anyway. It’s certainly no life for a fox.