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America has come this close to collective immunity.
Last May, “we had enough vaccination and natural immunity to have practically reached a population level of immunity,” said Dr Eric Topol. “We were going down to less than 10,000 cases a day. We looked good.
Then the delta variant moved the goal posts.
With the original version of the virus that causes COVID-19, America’s current vaccination rate of around 65% would have been enough to stop the spread.
“If we were to deal with the original, we have enough vaccines for the full-scale pandemic to be over in this country,” said Dr Joshua Schiffer, physician and mathematical modeling expert who studies infectious diseases at Fred Hutchinson. Cancer Research. Center in Seattle.
Unfortunately, the now dominant delta strain is more than twice as contagious and requires more people to be immunized by vaccination or a previous infection for the virus to stop spreading, experts say.
“Now we need 85 to 90% vaccinated against delta,” said Topol, vice president of research at Scripps Research in La Jolla, Calif., And national expert on the use of data in medical research. .
It is not an impossible number. In countries like Portugal, Singapore and the United Arab Emirates, more than 80% of the total population is now vaccinated, and cases and deaths are on the decline.
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This seems unlikely in the United States, where only 55% of the total population is fully vaccinated, and 12% of Americans say they are categorically opposed to it.
Herd immunity is now out of reach, said Stephen Kissler, an infectious disease researcher at Harvard TH Chan School of Public Health.
“I don’t think it’s realistic,” he said.
What is collective immunity?
The concept of herd immunity is simple: when disease invades a herd of animals, those that survive become immune. Eventually enough animals have what is called natural immunity, and the disease has so few animals to infect that it either dies or subsides.
Much ink was spilled at the start of the pandemic when various politicians and even nations suggested that if young and healthy people caught mild cases and recovered, there would be enough immunity for the virus is no longer circulating and vulnerable people are protected.
This was before vaccines were available, and the UK, Sweden, Brazil and the US under the Trump administration have championed the idea to varying degrees.
At one extreme was a group, which now included the Florida Surgeon General, who issued the Great Barrington Declaration in October 2020. He called on the world to end lockdowns and other transmission prevention measures and adopt collective immunity for COVID-19 to protect vulnerable people while allowing economies to thrive.
The idea is quickly denounced. With a death rate at the time of 1%, COVID-19 would have had to kill 3.2 million Americans for enough people to be infected to achieve herd immunity.
For a while, the arrival of COVID-19 vaccines changed the math. If two-thirds of Americans had been vaccinated in the spring, the virus would have had so few new people to infect that it could have been largely stopped.
Then the delta variant hit.
At the same time, new data began to show that natural immunity was not as protective as vaccination, and the benefits of injections began to wear off after about six months.
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More than a third of COVID-19 infections do not result in any protective antibodies, said Dr. Mark Rupp, an infectious disease expert at the University of Nebraska Medical Center.
“I wish it wasn’t true,” Rupp said. Many of his patients are convinced that having recovered from COVID-19 is all the defense they need.
The good news is that for people who have recovered from COVID-19, a single dose of the vaccine provides excellent immunity, Topol said.
“You can’t replicate that with any vaccine we have,” he said. “It’s quite extraordinary.”
So far, Rupp has not been very successful in convincing his vaccine-resistant patients to get vaccinated.
“I begged people,” he said.
When will the pandemic end?
With 55% of Americans fully vaccinated and at least 30% cured of COVID-19 at least once, how is it possible that the pandemic could increase in so many places yet?
America is a big country, and even a small number is a lot of people. While it is difficult to determine the number of people not exposed to COVID-19, whether through infection or vaccination, experts likely put it at around 15% of the American population. That’s nearly 50 million people – many to fall ill again, said Harvard’s Kissler.
It’s also becoming clear that COVID-19 is not “one and done,” said Lauren Ancel Meyers, professor of statistics and data science and director of the COVID-19 Modeling Consortium at the University of Texas at Austin.
Reinfection and breakthrough cases change the sensitivity landscape as immunity wanes.
As of October 1, daily COVID-19 deaths in the United States were 1,479, according to the Centers for Disease Control and Prevention.
“I find it humiliating that the remaining percentage, 15%, is still enough to overwhelm our healthcare system,” Schiffer said.
Experts say endemic COVID-19 could make virus ‘manageable’
The optimistic expectation, experts say, is that the pandemic will die out and the virus will become one of many endemic viruses around the world that continue to circulate but cause far less illness and death..
This is predicted to grow into an infection that still sweeps through the adult population in the winter, making some of them sick but usually only causing severe illness in the very old, those with weakened immune systems, and non-pregnant women. vaccinated, said editor-in-chief Dr Gregory Poland. -in chief of the journal Vaccine.
“Once we get to the point where everyone has been exposed or vaccinated and if – and this is a big if – COVID does what other respiratory illnesses do, it can be a manageable illness,” said Jeffrey Shaman, epidemiologist at Columbia University.
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Ideally, babies and toddlers would get it several times before they get to kindergarten, experts say. For the vast majority, COVID-19 is reportedly mild as it is today for most young children. By the time they start school, they would have pretty strong immune protection.
The COVID-19 vaccine would become one of the routine childhood vaccinations, likely requiring multiple doses and possible boosters if new variants emerge, experts say.
Much like the flu, COVID-19 in the northern hemisphere is expected to be an illness that appears during the colder months.
In the event of infection, vaccinated adults would usually have mild or even asymptomatic cases. Unvaccinated adults are more at risk of contracting serious illness. With age, the immune system becomes less robust, so annual injections of COVID-19 would be especially important for people over 65 and people with reduced immunity.
COVID-19 would likely continue to mutate as well. Some years it would be very light, others more severe.
COVID-19 is still evolving
But will this virus follow the typical path of others we come to live with?
“That’s the trillion dollar question,” the Columbia shaman said.
There is no guarantee with SARS-CoV-2, which can mutate so quickly. The worst-case scenario is that it evolves into something even more dangerous or more contagious than the delta.
“All that has to happen is for a new variant with a bigger immunity loophole to emerge, and we are starting from scratch,” Poland said.
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Public health experts have been concerned for years about a virus with infectivity of SARS-CoV-2 and death rate from Middle East respiratory syndrome coronavirus (MERS-CoV), which is fatal at 32 %.
Learning to live with COVID-19 means accepting uncertainty and always staying vigilant for what might happen, said Rustom Antia, professor of population biology at Emory University.
“Barring a miracle,” Schiffer added, “COVID will be a part of our lives for the rest of our lives.”
Contact Weise at [email protected]
This article originally appeared on USA TODAY: Is collective immunity against COVID still possible? Experts say endemic is more likely
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