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Experts say it’s likely that one version of the disease will persist for years. But what that will look like in the future is less clear.
Will the coronavirus, which has already killed more than 2 million people worldwide, finally be eliminated by a global vaccination campaign, like smallpox? Will dangerous new variants escape vaccines? Or will the virus stick around for a long time, turning into a slight annoyance, like the common cold?
Eventually, the virus known as SARS-CoV-2 will become yet “another animal in the zoo”, joining the many other infectious diseases that mankind has learned to live with, predicted Dr. T. Jacob John, who studies viruses and was at the forefront of India’s efforts to fight polio and HIV / AIDS.
But no one knows for sure. The virus is evolving rapidly and new variants are appearing in different countries. The risk of these newer variants was highlighted when Novavax Inc. discovered that the company’s vaccine did not work as well against the 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 become able to escape current tests, treatments and vaccines.
For now, scientists agree on the immediate priority: vaccinating as many people as possible as quickly as possible. The next step is less certain and depends largely on the strength of immunity offered by vaccines and natural infections and for how long.
“Are people going to be prone to repeated infections frequently? We don’t have enough data to know yet,” said Jeffrey Shaman, who studies viruses at Columbia University. Like many researchers, he thinks the chances of vaccines providing lifelong immunity are slim.
If humans are to learn to live with COVID-19, the nature of this coexistence depends not only on the duration of immunity, but also on how the virus evolves. Will it mutate significantly each year, requiring annual injections, like the flu? Or will it appear every few years?
This question of what happens next drew Emory University virologist Jennie Lavine, who co-authored a recent article in Science that projected a relatively optimistic scenario: After most people were exposed to virus – either through vaccination or surviving infections – the pathogen “will continue to circulate, but will mainly cause only mild illness,” such as a routine cold.
While acquired immunity to other coronaviruses – like those that cause the common cold or SARS or MERS – wanes over time, symptoms upon reinfection tend to be milder than the first illness, said Ottar. Bjornstad, co-author of the scientific article that studies viruses. at Pennsylvania State University.
“Adults tend not to have very bad symptoms if they’ve been exposed before,” he said.
The Science article’s prediction is based on an analysis of the behavior of other coronaviruses over time and assumes that SAR-CoV-2 continues to evolve, but not rapidly or drastically.
The 1918 influenza pandemic could offer clues to the evolution of COVID-19. This pathogen was an H1N1 virus whose genes came from birds, not a coronavirus. At the time, no vaccine was available. The United States Centers for Disease Control and Prevention estimates that one-third of the world’s population has been infected. Eventually, after the death or immunity of those infected, the virus stopped spreading rapidly. It then mutated into a less virulent form, which experts say continues to circulate seasonally.
“Very often the offspring of influenza pandemics become the mildest seasonal influenza viruses we have known for many years,” said Stephen Morse, who studies viruses at Columbia University.
It is not yet clear how future mutations in SARS-CoV-2 will shape the trajectory of the current disease.
As new variants emerge – some more contagious, others more virulent, and others perhaps less vaccine-responsive – scientists are reminded of how little they know about the future of the virus yet, Mark said. Jit, who studies viruses at the London School of Hygiene and Tropical Medicine.
“We’ve only known about this virus for about a year, so we don’t yet have data to show how it behaves over five or ten years,” he said.
Of the more than 12 billion coronavirus vaccines made in 2021, rich countries have purchased around 9 billion and many have options to purchase more. This inequality is a threat because it will force poorer countries to wait longer for the vaccine, during which time the disease will continue to spread and kill people, said Ian MacKay, who studies viruses at the University of Queensland. .
The fact that some vaccines appear to be less effective against the newer strains is worrisome, but because vaccines offer some protection, vaccines could still be used to slow or prevent the spread of the virus, said Ashley St. John, who studies the systems. immune systems at Duke-NUS Medical School in Singapore.
Dr Gagandeep Kang, an infectious disease expert at Christian Medical College in Vellore in southern India, said the evolution of the virus raises new questions: At what stage does the virus become a new strain? Will countries have to revaccinate from scratch? Or could a booster dose be given?
“These are questions that you will need to answer in the future,” Kang said.
The future of the coronavirus may contrast with other highly contagious diseases that have been largely defeated by vaccines that confer lifelong immunity – like measles. The spread of measles decreases after many people are vaccinated.
But the dynamics change over time with new births, so outbreaks tend to occur in cycles, said Dr Jayaprakash Muliyil, who studies outbreaks and advises India on virus surveillance.
Unlike measles, children infected with COVID-19 do not always have clear symptoms and could still transmit the disease to vulnerable adults. This 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 incapable for months, Kang said.
“Quantifying this damage” – how many people cannot do manual labor or are so exhausted that they cannot concentrate – is essential to understanding the full consequences of the disease.
“We haven’t had a lot of illnesses that have affected people on a scale like this,” she said.
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Larson reported from Washington.
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The Associated Press’s Department of Health and Science receives support from the Department of Science Education at the Howard Hughes Medical Institute. The AP is solely responsible for all content.
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