Scientists predict that once immunity is widespread among adults, the virus rampaging across the globe will resemble the common cold.
Researchers envision what a post-vaccine world might look like – and what they see is comforting as millions are inoculated against the Coronavirus.
The Coronavirus is here to stay, but after most adults become immune – following natural infection or vaccination – it will be no more of a threat than the common cold, according to a study published in Science on Tuesday.
Because the virus is an unfamiliar pathogen, it can overwhelm the adult immune system, which has not been trained to fight it. Once everyone has been exposed to either the virus or vaccine, that will no longer be the case.
Since children are constantly exposed to pathogens that are new to their bodies, they are more adept at fending off Coronavirus than adults. According to the study, the virus will eventually only affect children younger than 5 and only cause sniffles – or no symptoms at all.
This means the Coronavirus will become endemic, a pathogen that circulates at low levels and rarely causes serious illness.
“How quickly a disease spreads, and how quickly vaccination is implemented, determines how long it takes to reach this kind of endemic state,” said Jennie Lavine, a postdoctoral fellow at Emory University in Atlanta.
Getting everyone exposed to the vaccine for the first time is the key to success.
For clues about the fate of the new pathogen, Lavine and her colleagues examined six other human coronaviruses – four that cause the common cold, plus SARS and MERS.
Coronaviruses cause the common cold, but only mild symptoms. People became severely ill from SARS in 2003 and MERS in 2012, but they did not spread widely.
Doctor and her colleagues hypothesized that the new virus is the most similar to the endemic common cold coronaviruses.
Researchers found that on average, children are first infected with common cold coronaviruses between the ages of 3 and 5. It is possible for people to become infected again and again after that age, which boosts their immunity and keeps the viruses in circulation. However, they do not get sick.
Researchers predict a similar future for the new Coronavirus.
Doctor said it could take a few years to decades of natural infections for the Coronavirus to become endemic, depending on how quickly the virus spreads.
Without a vaccine, the fastest path to endemic status is also the most dangerous. In exchange for population immunity, widespread illness and death would be the price.
The faster people can be immunized, the better. Vaccines completely alter that calculus. By implementing an efficient vaccination program, the timeline for the Coronavirus becoming endemic could be shortened to a year, or even six months.
The vaccines may not be able to eradicate Coronavirus, however, according to Doctor. In our environment, the virus will become a permanent resident, albeit one that is more benign.
According to other experts, this scenario is not just plausible, but likely as well.
“I totally agree with the paper’s overall intellectual construct,” said Shane Crotty, a virologist at the La Jolla Institute for Immunology.
When vaccines prevent people from transmitting the virus, “it becomes a lot more like the measles situation, where you vaccinate everyone, including kids, and the virus is no longer spreading,” Doctor said.
Vaccines are likely to prevent illness, but not necessarily infection and transmission, he said. As a result, the Coronavirus will continue to circulate.
“The vaccines we have now won’t provide sterilizing immunity,” the kind needed to prevent infection, said Jennifer Gommerman, an immunologist at the University of Toronto.
Coronavirus infection results in a strong immune response in the nose and throat. With the current vaccines, Doctor explained, “you’re not getting a naturally occurring immune response in your upper respiratory system, but an injection in your arm.” This increases the likelihood that infections will still occur after vaccination.
Ultimately, Doctor’s model assumes that the new coronavirus is similar to the common cold coronavirus. Doctor, an epidemiologist at Harvard T.H. Chan School of Public Health in Boston, cautioned that assumption may not hold up.
“We don’t know what other Coronavirus infections can do to an older, naive person,” Doctor said. The term nave refers to an adult whose immune system has not been exposed to the virus.
Alternatively, the virus may come to resemble the seasonal flu, which is mild some years and deadly others, he said. Coronavirus variants that evade the immune system may also complicate matters.
“I’d put a lot of money on their prediction that it will become like common cold coronaviruses,” Doctor said. “But I don’t think it’s absolutely certain.”
It is unclear when or how the common cold coronaviruses first appeared, but some scientists are revisiting a theory that OC-43, one of the four common cold coronaviruses, may have caused a pandemic in 1890 that killed about one million people worldwide.
Andre Veillette, an immunologist at Montreal Clinical Research Institute in Canada, suggested that humans developed low-grade, broad immunity to OC-43 that ended the pandemic. Currently, this Coronavirus circulates peacefully in the community.”