SEATTLE — Early in the pandemic, many people seized on the hope that Covid-19 could be stopped in its tracks and buried for good once vaccines rolled out.
But hope for a zero-Covid country fizzled for most scientists long ago.
“Everyone has stopped talking about getting rid of Covid,” Dr. Elizabeth Halloran, an epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle, said of her fellow researchers. “It’s not going away, and that means it’s going to be endemic.”
Most scientists now expect the virus to circulate indefinitely with lower and more predictable case numbers — a status known as endemicity. That would make the coronavirus like many other viruses that humanity has learned to deal with, such as influenza. It remains unclear, however, whether the coronavirus will remain a greater health risk than other endemic respiratory viruses.
There are some indications that government and public health officials are already operating with that idea in mind. The latest wave of the omicron variant has served not only as a reminder that the coronavirus is still mutating in unexpected ways, but also as a signpost: Federal messaging and local government action, which once focused on stopping the virus’s spread and relied upon extreme measures like local lockdowns, is now centered on reducing risk and allowing the vaccinated and the boosted to go on with relatively normal lives with precautions.
With Covid expected to become a fixture — and considering how fast the omicron variant spreads — some infectious disease experts now think most everyone could be infected during their lifetimes.
“It seems to me it’s almost inevitable you’re going to become infected,” said Dr. Francis Riedo, an infectious disease physician at EvergreenHealth, a hospital system in Kirkland, Washington. “The real question is how severe that infection is going to be.”
Even if endemic Covid becomes inevitable, however, it doesn’t mean people should stop taking preventive measures, experts say. Instead, they are beginning to consider a future in which Covid precautions, such as masking and occasional encouragement to socially distance, could become somewhat common. Vaccinations would remain central, as would precautions for vulnerable people.
And in the near term, as the omicron variant rages, it remains critical that people — including the vaccinated — try to avoid becoming infected now, when the pandemic is spiking. The health care system could soon be under siege, hospital workers are exhausted, and there aren’t enough treatment tools, like monoclonal antibodies and antiviral pills.
“There’s definitely a responsibility to the community,” Riedo said. “If you look at the country, there are huge swaths unvaccinated and not infected yet but will be. And what can we do to help them?”
A virus becomes endemic as people grow overall immunity to a disease through vaccination or infection. Waning immunity keeps the virus from dying out completely.
For an endemic disease, every person who is infected transmits the virus to one additional person on average. But it’s a “dynamic equilibrium,” Halloran said, and the prevalence of the virus can wax and wane depending on factors like the season.
No model can predict how soon society could make the transition to endemicity, said Sergei Maslov, a professor of bioengineering at the University of Illinois at Urbana-Champaign, whose research suggests that ever-changing social interactions prevent pathogens from dying out and pushes them toward becoming endemic.
“Mutations are pretty unpredictable at this point, and we don’t know what will happen after omicron,” he said.
It typically takes a few years for a new viral pathogen to move from pandemic to endemic, said Maslov’s research partner, Alexei Tkachenko, a scientist at Brookhaven National Laboratory in Long Island, New York.
“Eventually, yes, there will be some sort of repeated pattern, an average level of prevalence of the epidemic,” Tkachenko said. “We cannot say it will be so low we don’t care.”
Pfizer executives said this week that they believe Covid will become endemic by 2024. The director of the National Institute of Allergy and Infectious Diseases, Dr. Anthony Fauci, wrote last week with colleagues that the virus is unlikely to be eradicated and that they expect “periodic outbreaks and endemics.” A survey in February in the journal Nature found that nearly 9 of 10 researchers working on the coronavirus thought Covid would become endemic.
Endemic diseases often settle into more predictable and stable patterns. Influenza, for example, spikes somewhat predictably during colder months. But researchers can’t say for sure how damaging an endemic level of Covid could become.
“The really open question for me — or maybe for public health or all of us — is when it becomes endemic and people become infected, how much severe disease and death does it cause?” Halloran said.
An endemic version of Covid could look somewhat similar to the flu, according to a projection by Trevor Bedford, a computational biologist at the Fred Hutchinson Cancer Research Center.
Bedford said he thinks endemic Covid could mean that most people would be infected about every three years, on average, with most cases quite mild.
Bedford’s back-of-the-napkin math — when the delta variant was the primary strain — suggested that 50,000 to 100,000 people could die in the U.S. every year from endemic Covid, according to a presentation he shared this fall. In the decade that preceded Covid, influenza caused 12,000 to 52,000 deaths a year, according to statistics from the Centers for Disease Control and Prevention.
Long Covid, a poorly understood disease that follows infection, could increase the social costs of the endemic Covid.
Riedo, an infectious disease physician, said the comparison to flu makes sense. Vaccination will be key to protecting vulnerable groups.
“With Covid, even if you’re vaccinated, some people are going to die, and the average age of those individuals is in their 80s,” Riedo said. “They have multiple comorbidities. They can’t tolerate a small perturbation in their physiology.”
Those who are unvaccinated and die of Covid tend to be younger by 10 to 15 years on average, with fewer health problems, Riedo said, adding that the same holds true for influenza.
Endemic Covid won’t affect everyone equally. Immunosuppressed people might not benefit as much from vaccinations and could need additional protection to reduce the risk of endemic Covid.
Riedo outlined a potential treatment plan for immunosuppressed people, who make up 4 percent to 5 percent of the U.S. population: “Every six months, you go in to get antibodies, and you have rapid tests available to them, and if you’re positive, you start them on new medications,” such as drugs that help inhibit viruses from reproducing.
If risks are more significant during spikes of endemic Covid, layers of protection, like masks and distancing, could still prevent infection and help manage risk, particularly for at-risk populations.
“Covid is not the first time they’ve had to think about double layers of protection or had to think about how to protect themselves during epidemics or environments that put them at risk,” said Erin Sorrell, an assistant professor of microbiology and immunology at Georgetown University in Washington, D.C. “Getting the common cold, the flu, measles, getting anything would be an issue for their health and safety.”
Not every virus becomes endemic or remains that way.
Strict control measures of the first SARS virus, which didn’t spread asymptomatically, allowed health officials to effectively eradicate it. The virus that causes smallpox was eradicated through worldwide vaccination efforts.
Some experts still believe eliminating the coronavirus country by country could be possible, although it would take huge investments and the costs might not outweigh the benefits.
Four other coronaviruses circulate in humans and cause common colds. Scientists suspect that they might have developed out of pandemics before they weakened in severity as people gained immunity.
But this is the first time researchers are measuring a coronavirus on a path toward becoming endemic. More surprises could be in store.
“Who would have thought of omicron?” Halloran said. “Is that in your crystal ball?”