Experts say it is likely that some version of the disease will linger for years. But what it will look like in the future is less clear.
Will the coronavirus, which has already killed more than 2 million people worldwide, eventually be eradicated by a global vaccination campaign like smallpox? Will dangerous new variants dodge vaccines? Or does the virus linger for a long time and turn into a mild annoyance, like a cold?
Eventually, the virus known as SARS-CoV-2 will become “another animal in the zoo” again, joining the many other infectious diseases that humanity has come to live with, Dr. T. Jacob John, who studies viruses and is at the helm of India’s efforts to tackle polio and HIV / AIDS.
But no one is sure. The virus is evolving rapidly and new variants are emerging in different countries. The risk of these new variants was underlined when Novavax Inc. found that the company’s vaccine didn’t work as well against mutated versions circulating in Britain and South Africa. The more the virus spreads, experts say, the more likely it is that a new variant will be able to evade current tests, treatments, and vaccines.
For now, scientists are in agreement on the immediate priority: vaccinate as many people as possible as soon as possible. The next step is less certain and depends largely on the strength of the immunity that vaccines and natural infections provide and how long it lasts.
“Do people regularly become victims of repeated infections? We don’t have enough data to know yet,” said Jeffrey Shaman, who studies viruses at Columbia University. Like many researchers, he believes that vaccines are unlikely to confer lifelong immunity.
If people are to learn to live with COVID-19, the nature of that coexistence depends not only on how long the immunity lasts, but also on how the virus evolves. Will it mutate significantly each year, requiring annual injections, as with the flu? Or does it show up every few years?
This question of what happens next attracted Jennie Lavine, a virologist at Emory University who is co-author of a recent paper in Science that projected a relatively optimistic scenario: After most people are exposed to the virus – either through vaccination or by surviving infections – the pathogen “continues to circulate, but usually causes only a mild illness”, such as the common cold.
While the immunity gained by other coronaviruses – such as those that cause a cold or SARS or MERS – diminishes over time, the symptoms with reinfection are usually milder than with the first disease, said Ottar Bjornstad, a co-author of the Science paper. that studies viruses. from Pennsylvania State University.
“Adults don’t tend to have very bad symptoms if they’ve already been exposed,” he said.
The prediction in the Science paper is based on an analysis of how other coronaviruses have behaved over time and assumes that SAR-CoV-2 will continue to develop, but not quickly or radically.
The 1918 flu pandemic could provide clues to the course of COVID-19. That pathogen was an H1N1 virus with genes from birds, not a coronavirus. At the time, no vaccines were available. The U.S. Centers for Disease Control and Prevention estimate that one-third of the world’s population has become infected. Eventually, after infected people died or developed immunity, the virus quickly stopped spreading. It later mutated into a less virulent form, which experts say continues to circulate seasonally.
“Very often the descendants of influenza pandemics become the milder seasonal influenza viruses we have experienced for years,” said Stephen Morse, who studies viruses at Columbia University.
It is not yet clear how future mutations in SARS-CoV-2 will determine the pathway of current disease.
As new variants emerge – some more contagious, others more virulent, and some possibly less sensitive to vaccines – scientists are reminded how much they don’t yet know about the future of the virus, said Mark Jit, who studies viruses at the London School of Hygiene and Tropical. medicine.
“We’ve only been aware of this virus for about a year, so we don’t have data to show its behavior in five or ten years,” he said.
Of the more than 12 billion coronavirus vaccination shots taken in 2021, wealthy countries will have bought about 9 billion, and many have options to buy more. This inequality is a threat as it will mean that poorer countries will have to wait longer for the vaccine. During this time, the disease will continue to spread and kill people, said Ian MacKay, who studies viruses at the University of Queensland.
That some vaccines appear less effective against the new strains is worrying, but since the injections provide some protection, vaccines can still be used to slow or stop the spread of the virus, said Ashley St. John, who studies immune systems at Duke -NUS Medical. School in Singapore.
Dr. Gagandeep Kang, an infectious disease expert at Christian Medical College in Vellore, South India, said the evolution of the virus raises new questions: At what stage does the virus become a new strain? Will countries have to vaccinate all over again? Or can a booster dose be given?
“These are questions you will have to answer in the future,” said Kang.
The future of the coronavirus may contrast with other highly contagious diseases that have been largely warded off by vaccines that provide lifelong immunity – such as measles. The spread of measles decreases after many people are vaccinated.
But the dynamics change over time with new births, so outbreaks usually come in cycles, Dr. Jayaprakash Muliyil, who studies epidemics and advises India on virus surveillance.
Unlike measles, children infected with COVID-19 do not always show obvious symptoms and can still transmit the disease to vulnerable adults. That means countries cannot let their guard down, he said.
Another unknown is the long-term impact of COVID-19 on patients who survive but are incapacitated for work for months, Kang said.
The “quantification of this damage” – how many people are unable to do manual labor or are so exhausted that they cannot concentrate – is essential to understand the full consequences of the disease.
“We haven’t had many diseases that have affected people on such a scale,” she said.
Larson reported from Washington.
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