Have you heard that the Covid vaccine turns you into a vampiric monster — and that the proof is right there in the 2007 Will Smith movie “I Am Legend”?

This conspiracy theory appeared online last year and spread so widely that Reuters actually ran a fact check debunking it (and clarifying the plot). One of the screenwriters of the movie also felt compelled to tweet that it was fictional.

While such ludicrous disinformation may seem peculiar to the social media era, it’s also a throwback to the origins of our most famous monster.

No, the first vampires did not appear in books or movies. They weren’t debonair Transylvanian counts or good-looking, disaffected teenagers. Rooted in folklore, they were symbols of epidemics — and a plausible explanation for disease, at least for the time.

Some of the earliest accounts date back to 11th- and 12th-century Europe when outbreaks of tuberculosis, rabies and other diseases were blamed, in part, on vampires.

William of Newburgh, a medieval English historian, recorded one account of a town devastated by such a monster, who was accused of filling “every house with disease and death by its pestiferous breath.”

The offending creature, which came out of his grave at night, was eventually dug up and stabbed by two brothers “who had lost their father by this plague,” Newburgh wrote. Blood flowed out of the monster as if it were a “leech filled with the blood of many persons”; with the monster defeated, “the pestilence which was rife among the people ceased.”

If such scapegoating sounds unlikely, consider life during those medically primitive times. People would die of disease. Then their loved ones would be exposed to them before they were buried, causing more sickness and death. Because of the incubation period of certain diseases and the ignorance about how microscopic viruses traveled, no one could understand the slow-moving catastrophe.

“When people lack science to explain things, they rely on magic and religion,” said Stanley Stepanic, an assistant professor of Slavic languages and literature at the University of Virginia who teaches a popular course on “Dracula.” “When there was a void in knowledge about disease, the vampire filled in.”

These early vampires tended to have bloody mouths, bloated stomachs, bad breath — more like what we now know as zombies. It wasn’t until the 19th century, as they became fixtures in weird fiction, that vampires were more likely to be wealthy creeps in formal wear.

During this period, the emergence of vaccines became a polarizing subject: The first compulsory vaccination laws were enacted in England, sparking a backlash movement that used the vampire as a metaphor for bodily violation, with fangs representing surgical instruments.

The medium then was pamphlets, not social media. One fear-mongering handbill, “The Vaccination Vampire,” from 1881, for example, pushed the claim that vaccinations would lead to “degradation and extinction,” and were a source of “universal pollution.”

“The vampire expressed fears about cutting into and polluting the body,” said Nadja Durbach, a historian and the author of the book “Bodily Matters: The Anti-Vaccination Movement in England, 1853-1907,” adding that there was real fear vaccinations would disrupt the right balance of humors, those bodily fluids (blood included) that were considered very important to one’s health back then. And anything that interfered with blood terrified people.

“The anti-vaccination movement is an important context for ‘Dracula,’” Ms. Durbach said.

Dracula and His Legacy

When Bram Stoker wrote his culturally transformative novel in 1897, about a Transylvanian nobleman who leaves his castle to travel to modern-day London in search of fresh blood, he certainly knew about vampire folklore as well as the anti-vaccination movement, and was working on some of the same fears.

Along with giving Dracula the ability to shapeshift into a bat, he expanded the range of anxieties associated with the vampire, turning it from a symbol of sickness into one of repressed desire. As Stephen King put it in his book “Danse Macabre,” “Stoker revitalized the vampire legend largely by writing a novel that fairly pants with sexual energy.”

That is not to say the Count was particularly handsome. With hairy palms, arched nostrils and sharp teeth, he was more animalistic than the smooth villain he would later become onscreen, in Hollywood adaptations.

The first “Dracula,” the German expressionist classic “Nosferatu,” shot the year after the influenza pandemic ended, is haunted by disease, mass death and even a quarantine in a small town. With his rodent-like teeth, elongated fingers and skeletal silhouette, the terrifying vampire not only looks like a rat, widely known as the deliverer of the Black Plague — he also exits his coffin surrounded by them.

A decade later, Bela Lugosi transformed the image of the vampire from a beast to an alluring European count in the Universal film “Dracula.” His voice, and haircut, remain vampire clichés today, but his glaring intensity and charisma is what really had an impact. The actors who followed him brought even more sensuality to the role, working on our desires as well as our fears.

Seductiveness defined 20th-century vampires, from the glamorous Southern Gothic of Anne Rice novels to the bosomy Victorian world of Hammer Film of the 1960s and ’70s. By the next decade, the hot vampire genre merged with the relatable teen comedy in “The Lost Boys,” which led to “Buffy the Vampire Slayer” and then “Twilight,” the commercial apex of domesticated, misunderstood vampires.

Bloodsuckers were no longer monstrous others. Now they were romantic outsiders and even heroes fighting their own natures for the love of others. HBO’s “True Blood” radically shifted vampires from wealthy elites of Victorian literature to an oppressed class in the American South, struggling for equal rights (and still having a lot of sex).

The tradition of sexy vampires is still alive with the campy new Netflix movie “Night Teeth,” set amid the neon-lighted night life of contemporary Los Angeles. The slick movie involves the breaking of an ancient truce among supernatural monsters, but its main purpose seems to be to set up stylishly bloody action and a scene with Megan Fox and Sydney Sweeney, whose repartee represents a passing of the torch from one generation of sex symbol to another.

Still, while sex has long been a simmering subtext to this monster, the vampire has proved to be remarkably flexible, metaphorically, evolving to reflect acute topical anxieties within the culture.

Amazon’s “Black as Night,” a vampire story for the Black Lives Matter moment, builds its mythology on a history of white supremacy, with a story of a teenage girl fighting vampires in New Orleans. (Part of a new crop of racially progressive horror, this movie’s antecedents include the 1972 “Blacula,” about an 18th-century African prince enslaved by Count Dracula on a diplomatic mission to Transylvania designed to curb the slave trade.)

The stupendous comedy “What We Do in the Shadows” is too smart to let any metaphorical meaning get in the way of good jokes. But as its hapless vampires stumble into positions of leadership in the Vampiric Council in the current season, they have become perfect symbols for our broken, ineffectual political system. The core joke of this show is a sendup of the history of glamorous bloodsuckers. By utilizing the same documentary conceit as “The Office” to follow the boring lives of vampires living on Staten Island, this TV series captures an often overlooked truth about eternal life: It gets tedious.

The vampires navigate mundane struggles, play cornhole and suffer from depression. In the most ingenious character of Colin Robinson (Mark Proksch), the show invents a new kind of monster, the energy vampire, who sucks the life out of people by boring them to unconsciousness with terrible jokes and mansplaining. The “Hotel Transylvania” series (the fourth film arrives in January) also works off a demystifying playbook, albeit through the banality of family life.

Many more vampire shows are on the way, including remakes of the 1970s TV series “Salem’s Lot,” Ms. Rice’s novel “Interview With the Vampire” and the delicately drawn Swedish movie “Let the Right One In.” “The Lost Boys” is also being rebooted.

Vampires are even invading the super hero genre with Marvel working on another “Blade,” starring Mahershala Ali, and “Morbias,” coming in January, in which Jared Leto plays a biochemist trying to cure himself of a blood disease who accidentally infects himself with a form of vampirism.

Boom Times for Blood Suckers

Whatever political and social fears vampire movies work on, the genre always cycles back to the theme of disease. During the AIDS epidemic in the 1980s and early ’90s, a virus passed through sexual encounter or by blood infusion took on new meaning in many vampire stories, and the specter of plague provided a subtext, if not something more overt, in movies like Francis Ford Coppola’s “Bram Stoker’s Dracula.”

The most influential vampire novel after “Dracula” is Richard Matheson’s 1954 book “I Am Legend,” the movie version of which became the subject of those recent anti-vaccination conspiracy theories.

The story focuses on the last man on Earth after a pandemic spreading airborne disease wipes out humanity, replacing some people with vampires. The cause was not a vaccine; it was an attempt to cure cancer, gone wrong.

Shifting the focus from bloodsucking to viral transmission, “I Am Legend” introduced modern apocalyptic horror, with its endless procession of hordes of rampaging monsters. George Romero cited it as the inspiration for his 1968 game-changer “Night of the Living Dead,” kicking off a new monster tradition of the zombie, which considering the zombified style of the original vampires, could be seen as more of a return to form.

One of the most common diseases explored in vampire movies is addiction, a theme of genre highlights including Kathryn Bigelow’s debut “Near Dark” and George Romero’s anti-vampire film “Martin” as well as the new shows streaming.

But more recent movies and shows also seem to be working on Covid-era fears of epidemics.

“Midnight Mass,” a portrait of a vampire infestation on a small island town, tells the story of a charismatic newcomer (Hamish Linklater) who takes over as a priest of a sleepy church, quickly drawing crowds to his magnetic sermons, while miraculous, bizarre and increasingly bloody events keep happening around him. The violence in this show is brutal, beginning with hundreds of dead cats washing up on the beach, assumed to be the result of illness.

And this season of “American Horror Story,” which also opens with some deceased animals, centers on a television writer whose career takes off when he starts drinking blood. The first warning of something being terribly wrong comes from a wonderfully unhinged Sarah Paulson, playing a pale, ranting woman known around town as Tuberculosis Karen. Her hacking cough may trigger Covid anxieties, but her nickname evokes a much older disease, tied to the birth of the myth of the vampire.

To scare audiences, artists must adapt. Fanged Europeans don’t terrify like they once did, but contagion does. As societal fears become oriented around the pandemic, what will happen to the future of the vampire?

Joe Dante, a veteran horror director, speculated that we have so much more to be scared of today than in recent years, both politically and medically, that “it may be difficult to go back to the purely supernatural approach.” But Larry Fessenden, who starred and directed in one of the best vampire movies of the 1990s, the intimate New York indie “Habit,” sees new opportunities for horror.

“The pandemic has heightened our fear of each other, of infection and contagion, invisible droplets delivering a cataclysmic blow to our physical beings, leading in turn to an atmosphere of deep mistrust and isolation,” he wrote in an email. “And always, there will be those who don’t believe the monster even exists. I think a wave of vampire stories that captures a claustrophobic preoccupation with death and paranoia may be filling our screens next.”