Coronavirus Will Resemble the Common Cold, Scientists Predict
Once immunity is widespread in adults, the virus rampaging across the world will come to resemble the common cold, scientists predict.
As millions are inoculated against the coronavirus, and the pandemic’s end finally seems to glimmer into view, scientists are envisioning what a post-vaccine world might look like — and what they see is comforting.
The virus is a grim menace now because it is an unfamiliar pathogen that can overwhelm the adult immune system, which has not been trained to fight it. That will no longer be the case once everyone has been exposed to either the virus or vaccine.
Children, on the other hand, are constantly challenged by pathogens that are new to their bodies, and that is one reason they are more adept than adults at fending off the coronavirus. Eventually, the study suggests, the virus will be of concern only in children younger than 5, subjecting even them to mere sniffles — or no symptoms at all.
In other words, the coronavirus will become “endemic,” a pathogen that circulates at low levels and only rarely causes serious illness.
“The timing of how long it takes to get to this sort of endemic state depends on how quickly the disease is spreading, and how quickly vaccination is rolled out,” said Jennie Lavine, a postdoctoral fellow at Emory University in Atlanta, who led the study.
“So really, the name of the game is getting everyone exposed for the first time to the vaccine as quickly as possible.”
Dr. Lavine and her colleagues looked to the six other human coronaviruses — four that cause the common cold, plus the SARS and MERS viruses — for clues to the fate of the new pathogen.
The four common cold coronaviruses are endemic, and produce only mild symptoms. SARS and MERS, which surfaced in 2003 and 2012, respectively, made people severely ill, but they did not spread widely.
While all of these coronaviruses produce a similar immune response, the new virus is most similar to the endemic common cold coronaviruses, Dr. Lavine and her colleagues hypothesized.
Reanalyzing data from a previous study, they found that the first infection with common cold coronaviruses occurs on average at 3 to 5 years of age. After that age, people may become infected again and again, boosting their immunity and keeping the viruses circulating. But they don’t become ill.
The researchers foresee a similar future for the new coronavirus.
Depending on how fast the virus spreads, and on the strength and longevity of the immune response, it would take a few years to decades of natural infections for the coronavirus to become endemic, Dr. Lavine said.
Life will return to normal only when society as a whole gains enough protection against the coronavirus. Once countries authorize a vaccine, they’ll only be able to vaccinate a few percent of their citizens at most in the first couple months. The unvaccinated majority will still remain vulnerable to getting infected. A growing number of coronavirus vaccines are showing robust protection against becoming sick. But it’s also possible for people to spread the virus without even knowing they’re infected because they experience only mild symptoms or none at all. Scientists don’t yet know if the vaccines also block the transmission of the coronavirus. So for the time being, even vaccinated people will need to wear masks, avoid indoor crowds, and so on. Once enough people get vaccinated, it will become very difficult for the coronavirus to find vulnerable people to infect. Depending on how quickly we as a society achieve that goal, life might start approaching something like normal by the fall 2021.
Yes, but not forever. The two vaccines that will potentially get authorized this month clearly protect people from getting sick with Covid-19. But the clinical trials that delivered these results were not designed to determine whether vaccinated people could still spread the coronavirus without developing symptoms. That remains a possibility. We know that people who are naturally infected by the coronavirus can spread it while they’re not experiencing any cough or other symptoms. Researchers will be intensely studying this question as the vaccines roll out. In the meantime, even vaccinated people will need to think of themselves as possible spreaders.
The Pfizer and BioNTech vaccine is delivered as a shot in the arm, like other typical vaccines. The injection won’t be any different from ones you’ve gotten before. Tens of thousands of people have already received the vaccines, and none of them have reported any serious health problems. But some of them have felt short-lived discomfort, including aches and flu-like symptoms that typically last a day. It’s possible that people may need to plan to take a day off work or school after the second shot. While these experiences aren’t pleasant, they are a good sign: they are the result of your own immune system encountering the vaccine and mounting a potent response that will provide long-lasting immunity.
No. The vaccines from Moderna and Pfizer use a genetic molecule to prime the immune system. That molecule, known as mRNA, is eventually destroyed by the body. The mRNA is packaged in an oily bubble that can fuse to a cell, allowing the molecule to slip in. The cell uses the mRNA to make proteins from the coronavirus, which can stimulate the immune system. At any moment, each of our cells may contain hundreds of thousands of mRNA molecules, which they produce in order to make proteins of their own. Once those proteins are made, our cells then shred the mRNA with special enzymes. The mRNA molecules our cells make can only survive a matter of minutes. The mRNA in vaccines is engineered to withstand the cell's enzymes a bit longer, so that the cells can make extra virus proteins and prompt a stronger immune response. But the mRNA can only last for a few days at most before they are destroyed.
Without a vaccine, the fastest path to endemic status is also the worst. The price for population immunity would be widespread illness and death along the way.
Vaccines completely alter that calculus: The faster people can be immunized, the better. An efficient vaccination rollout could shorten the timeline to a year, or even just six months, for the coronavirus to become an endemic infection.
Still, the vaccines are unlikely to eradicate the coronavirus, Dr. Lavine predicted. The virus will become a permanent, albeit more benign, inhabitant in our environment.
Other experts said this scenario was not just plausible but likely.
“The overall intellectual construct of the paper I fully agree with,” said Shane Crotty, a virologist at the La Jolla Institute for Immunology in San Diego.
If the vaccines prevent people from transmitting the virus, “then it becomes a lot more like the measles scenario, where you vaccinate everybody, including kids, and you really don’t see the virus infecting people anymore,” Dr. Crotty said.
It is more plausible that the vaccines will prevent illness — but not necessarily infection and transmission, he added. And that means the coronavirus will continue to circulate.
“It’s unlikely that the vaccines we have right now are going to provide sterilizing immunity,” the kind needed to prevent infection, said Jennifer Gommerman, an immunologist at the University of Toronto.
Natural infection with the coronavirus produces a strong immune response in the nose and throat. But with the current vaccines, Dr. Gommerman said, “you’re not getting a natural immune response in the actual upper respiratory tract, you’re getting an injection in the arm.” That raises the likelihood that infections will still occur, even after vaccination.
Ultimately, Dr. Lavine’s model rests on the assumption that the new coronavirus is similar to the common cold coronaviruses. But that assumption may not hold up, cautioned Marc Lipsitch, an epidemiologist at the Harvard T.H. Chan School of Public Health in Boston.
“Other coronavirus infections may or may not be applicable, because we haven’t seen what those coronaviruses can do to an older, naïve person,” Dr. Lipsitch said. (Naïve refers to an adult whose immune system has not been exposed to the virus.)
Another plausible scenario, he said, is that the virus may come to resemble the seasonal flu, which is mild some years and more lethal in others. New variants of the coronavirus that evade the immune response may also complicate the picture.
“Their prediction of its becoming like common cold coronaviruses is where I’d put a lot of my money,” Dr. Lipsitch said. “But I don’t think it’s absolutely guaranteed.”
When and how the common cold coronaviruses first appeared is a mystery, but since the emergence of the new coronavirus, some scientists have revisited a theory that a pandemic in 1890, which killed about one million people worldwide, may have been caused by OC-43, one of the four common cold coronaviruses.
“People have suggested that the human population developed a low-grade, broad immunity to OC-43 that terminated the pandemic,” said Andre Veillette, an immunologist at Montreal Clinical Research Institute in Canada. “This coronavirus currently broadly circulates in the community in a rather peaceful way.”