A virus that shows no signs of disappearing, variants able to evade the body’s defenses and waves of infections two or even three times a year – this may be the future of Covid-19, now fear some scientists.
The central problem is that the coronavirus has become more adept at reinfecting people. Already, people infected with the first variant of Omicron are reporting second infections with 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 within this year, researchers said in interviews. And a small fraction may have symptoms that persist for months or years, a condition known as Long Covid.
“It seems likely to me that this will be somewhat of a long-term pattern,” said Juliet Pulliam, an epidemiologist at the University of Stellenbosch in South Africa.
“The virus will continue to evolve,” she added. “And there will likely be a lot of people who will have very many reinfections throughout their lives.”
It’s difficult to quantify how often people are reinfected, in part because many infections go unreported. Dr. Pulliam and his colleagues have collected enough data in South Africa to say that the rate is higher with Omicron than seen with previous variants.
That’s not how it was supposed to be. Earlier in the pandemic, experts believed that immunity from vaccination or prior infection would prevent most reinfections.
The Omicron variant dashed those hopes. Unlike previous variants, Omicron and its many descendants appear to have evolved to partially evade 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 get infected with it 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 it’s going to turn out.”
The new variants have not altered 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 attention if they test positive for coronavirus. And a booster dose, like a previous bout with the virus, appears to decrease the risk of reinfection – but not by much.
At the start of the pandemic, many experts based their expectations of the coronavirus on the flu, the viral enemy with which they are most familiar. They predicted that, like the flu, there could be a big outbreak every year, most likely in the fall. The way to minimize its spread would be to vaccinate people before it arrives.
Instead, the coronavirus behaves more like four of its closely related cousins, circulating and causing colds all year round. When studying cold coronaviruses, “we saw people with multiple infections within a year,” said Jeffrey Shaman, an epidemiologist at Columbia University in New York.
If reinfection turns out to be the norm, the coronavirus “won’t just be this once-a-year winter thing,” he said, “and it won’t be a mild nuisance in terms of morbidity and mortality. this implies.”
Reinfections with earlier variants, including Delta, have occurred but were relatively infrequent. But in September the rate of reinfections in South Africa appeared to be accelerating and was markedly high in November when the Omicron variant was identified, Dr Pulliam said.
Reinfections in South Africa, as in the United States, may seem even more visible because so many people have already been vaccinated or infected at least once.
“Perception amplifies what is actually happening biologically,” Dr. Pulliam said. “It’s just that there are more people eligible for reinfection.”
The Omicron variant was sufficiently different 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 little modification to its genetic code.
“It’s actually a bit of a surprise to me,” said Alex Sigal, a virologist at the Africa Health Research Institute. “I thought we would need some kind of brand new variant to escape this one. But in fact, it seems not.
An infection with Omicron produces a weaker immune response, which seems to fade quickly, compared to infections with previous variants. Although the new versions of the variant are closely related, they vary enough from an immune standpoint that infection with one doesn’t leave much protection against the others – and certainly not after three or four months.
However, the good news is that most people re-infected with new versions of Omicron will not become seriously ill. At least for now, the virus hasn’t found a way to completely bypass the immune system.
“It’s probably as good as it gets for now,” Dr. Sigal said. “The big danger could come when the variant is completely different.”
Each infection can bring with it the possibility of a long Covid, the constellation of symptoms that can linger for months or years. It is too early to know how often an Omicron infection leads to long Covid, especially in vaccinated people.
To keep up with the evolution of the virus, other experts said, Covid vaccines would need to be updated faster, even faster than flu shots are every year. Even an imperfect match with a new form of coronavirus will further broaden immunity and provide some protection, they said.
“Every time we think we’ve been through this, every time we think we’ve got the upper hand, the virus is playing a trick on us,” Dr Andersen said. “The way to get it under control is not, ‘Let’s all get infected a few times a year and then hope for the best.’”