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 coronavirus is here to stay, but once most adults are immune — following natural infection or vaccination — the virus will be no more of a threat than the common cold, according to a study published in the journal Science on Tuesday.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.ImageA cell infected with the new coronavirus, taken from a patient sample.Credit…National Institutes of Health/EPA, via ShutterstockReanalyzing 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.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
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