How often can you be infected with the coronavirus?

A virus that shows no signs of disappearing, variants that are adept at evading the body’s defenses, and waves of infections two, maybe three times a year – this could be the future of Covid-19, some scientists now fear.

The central problem is that the coronavirus has become more apt to reinfect people. Already, those infected with the first Omicron variant are reporting second infections with the newer versions of the variant – BA.2 or BA2.12.1 in the United States, or BA.4 and BA.5 in South Africa.

These people could have a third or fourth infection even this year, researchers said in interviews. And some small fraction can have symptoms that persist for months or years, a condition known as Covid.

“It seems likely to me that this is a long-term pattern,” said Juliet Pulliam, an epidemiologist at Stellenbosch University in South Africa.

“The virus will continue to evolve,” he added. “And there will likely be many people getting many, many reinfections over the course of their lives.”

It is difficult to quantify how often people are reinfected, in part because many infections go unreported. Dr. Pulliam and his colleagues collected enough data in South Africa to say the rate is higher with Omicron than with previous variants.

This is not how it should be. At the beginning of the pandemic, experts thought that immunity to vaccination or previous infection would prevent most reinfections.

The Omicron variant dashed those hopes. Unlike earlier variants, Omicron and its many descendants appear to have evolved to partially avoid immunity. This leaves everyone – even those who have been vaccinated multiple times – vulnerable to multiple infections.

“If we manage it the way we manage it now, most people will be infected at least twice a year,” said Kristian Andersen, a virologist at the Scripps Research Institute in San Diego. “I would be very surprised if that’s not how things turn out.”

The new variants have not changed the fundamental utility of Covid vaccines. Most people who have received three or even just two doses will not get sick enough to need medical care if they test positive for the coronavirus. And a booster shot, like a previous bout with the virus, seems to lessen the chance of reinfection — but not by much.

At the beginning of the pandemic, many experts based their expectations of the coronavirus on the flu, the viral enemy most familiar to them. They predicted that, as with the flu, there could be a major outbreak each year, most likely in the fall. The way to minimize its spread would be to vaccinate people before their arrival.

Instead, the coronavirus is behaving more like four of its closely related cousins, which circulate and cause colds all year round. When studying common cold coronaviruses, “we saw people with multiple infections within a year,” said Jeffrey Shaman, an epidemiologist at Columbia University in New York.

If reinfection is the norm, the coronavirus “is not just going to be this once-a-year winter thing,” he said, “and it’s not going to be a mild nuisance in terms of morbidity and mortality. cause”.

Reinfections with earlier variants, including Delta, occurred but were relatively infrequent. But in September, the pace of reinfections in South Africa appeared to increase and was markedly high in November, when the Omicron variant was identified, Pulliam said.

Re-infections in South Africa, as in the United States, may seem even more noticeable because many have been immunized or infected at least once so far.

“Perception magnifies what is actually happening biologically,” said Dr. Pulliam. “It’s just that there are more people who are eligible for reinfection.”

The Omicron variant was different enough from Delta and Delta from earlier versions of the virus that some reinfections were to be expected. But now, Omicron appears to be developing new forms that penetrate immune defenses with relatively few changes to its genetic code.

“This is really a surprise to me,” said Alex Sigal, a virologist at the Africa Health Research Institute. “I thought we would need an entirely new variant type to escape this one. But actually, it seems not.”

An infection with Omicron produces a weaker immune response, which appears to subside rapidly, compared to infections with earlier variants. While the newer versions of the variant are closely related, they vary enough from an immunological standpoint that infection with one doesn’t leave much protection against the others — and certainly not after three or four months.

Still, the good news is that most people reinfected with new versions of Omicron will not become seriously ill. At least for now, the virus hasn’t found a way to fully bypass the immune system.

“That’s probably the best it can be for now,” said Dr. Follow “The big danger can come when the variant is completely different.”

Each infection can bring with it the possibility of Covid-19, the constellation of symptoms that can persist for months or years. It’s too early to know how often an Omicron infection leads to long-term Covid, especially in vaccinated people.

To keep up with the evolution of the virus, other experts said, Covid vaccines must be updated faster, even faster than flu shots each year. Even an imperfect match with a new form of coronavirus will still boost immunity and offer some protection, they said.

“Every time we think we’re over it, every time we think we’ve got the upper hand, the virus tricks us,” Andersen said. “The way to control it is not, ‘Let’s all get infected a few times a year and then hope for the best.’

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