Initial laboratory tests suggest that the new COVID-19 variant BA.2.86 may be less contagious and less immunocompromising than feared

Scientists around the world are conducting rapid laboratory experiments to try to understand the severely mutated BA.2.86 variant of the virus that causes COVID-19. Experts say the results, which are just beginning to appear, offer some reassurance.

Two groups — one in China and one in Sweden — have made public their findings, with more expected from the US as early as Monday. So far, initial results paint BA.2.86 as a paper tiger rather than the looming beast it first appeared to be, although that impression may change as more results become available.

BA.2.86, also known by the nickname Pirola, attracted worldwide attention because it looks completely different from any other variant of the coronavirus we have seen so far.

This new lineage has more than 30 changes in its spike protein compared to its closest ancestor, BA.2, and compared to the recently circulating XBB.1.5 lineage. It was an evolutionary leap on par with that made by the original Omicron variant, BA.1, when it was first launched almost two years ago – and everyone remembers how that happened.

During the Omicron wave, infections and hospitalizations in the United States reached the peak of the pandemic. The weekly deaths hit their second-highest peak, proof that even a more tame version of the virus can pose a serious threat if it unleashes a tidal wave of infections across the population. The vaccines had to be updated.

Omicron quickly overtook other COVID-19 variants and began developing its own offshoots – viruses we still struggle with. It became a lesson in how agile the virus can be and how fragile our defenses are in the face of such big changes.


The White House was so concerned about another Omicron-level event that earlier this year it quietly polled about a dozen experts on the chances that the world would witness one within the next two years. Most experts put the probability at 10 to 20%.

When BA.2.86 hit the scene in late July with eerie overtones of Omicron, variant hunters were spooked and researchers took action to learn more about the new lineage. So far it has spread to at least 11 countries, including the United States.

The country that has reported the highest number of incidents so far is Denmark, and experts say they are closely monitoring the situation there for signs of an increase.

But so far only about three dozen sequences from as many infected patients have surfaced in a global repository in the last month. Even though genetic surveillance is much less than it used to be, experts believe it would be obvious if BA.2.86 caught on.

“My friends, this is not the second appearance of Omicron. If that were the case, we can say with certainty that we would know by now,” said Dr. Bill Hanage, an epidemiologist and co-director of Harvard University’s Center for Communicable Disease Dynamics, in a social media post.

Now scientists are in the midst of lab experiments — either using copies of the actual virus isolated from patients or models of its spike proteins grafted onto the body of another virus — designed to help us better understand how well our immune systems and vaccines will recognize and fight off BA.2.86 family viruses.


In the first series of experiments, using the blood of vaccinated mice and vaccinated and recently infected people, researchers in China found that BA.2.86 actually looks very different to our immune system than previous versions of the virus that causes COVID-19 . and it’s able to escape some of our immunity.

Researcher Yunlong Cao from Peking University’s Biomedical Innovation Center said he found a two-fold decrease in our immunity’s ability to neutralize the BA.2.86 virus compared to XBB.1.5 family viruses from vaccination and recent infections.

A two-fold drop isn’t miraculous, but it’s not huge either. In comparison, an eight-fold decrease in the ability of vaccine-generated immunity to neutralize a new influenza virus is the yardstick scientists use to update the flu shot.

At the same time, the BA.2.86 virus was about 60% less infectious than the XBB.1.5 virus, which experts say may explain why it was found in so many different countries, albeit in small amounts.

“I would say that it will slowly spread among the population. It won’t be able to compete with other fast-growing variants,” Cao noted in an email to CNN, referring to variants like EG.5 and FL.1.5.1, which are currently being broadcast in the United States dominate.

In a second set of experiments, researchers at the Karolinska Institute in Sweden tested BA.2.86 with antibodies in the blood of human donors collected at two different time points, from late 2022, before the XBB variant emerged, and from late August.

The antibodies in the older samples weren’t effective at knocking out BA.2.86, but the blood samples drawn from donors just a week ago did a better job.

“Overall, it doesn’t appear to be nearly as extreme a situation as when Omicron originally appeared,” principal investigator Benjamin Murrell wrote in a social media post.

“It’s not yet clear whether BA.2.86 (or its progeny) will supplant the currently circulating variants, and I don’t think there’s any data yet on its severity, but our antibodies don’t seem completely powerless against it.” it,” he wrote.


Both studies have limitations. The researchers tested pseudoviruses, which are essentially models of what the BA.2.86 virus looks like, rather than the virus itself. Only a few samples from blood donors were used for the study from Sweden. And because these studies used blood donors from China and Sweden, they may not reflect the immunity of people in the US who may have been infected with a different mix of variants and immunized with different vaccines.

Still, experts said they were encouraged by these early results and eager to learn more in the coming days.

“The news is better than I expected,” said Dr. Ashish Jha, former White House COVID-19 response coordinator, in a social media post. “And it makes me even more encouraged that the new upcoming vaccine will have real utility against the current dominant variant (EG.5) as well as BA.2.86.”

The UK Health Safety Authority’s Variant Technical Group met last week to consider whether BA.2.86 should be reclassified from a ‘monitored variant’ to a ‘variant of concern’ in this country.

In an update released on Friday, the group concluded that BA.2.86 does not meet their definition of a variant of concern because they have no evidence that its profile represents a deleterious change in its biological properties or a growth rate that suggests it that it would move at least as fast or faster than currently circulating variants.

The group said two samples of the virus were being cultured in the UK and that data from those lab experiments were likely at least a week or two away. Meanwhile, they said they would be watching for results from international partners.

They, like the rest of the world, are waiting for BA.2.86 to show its cards.

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