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03:25 - Source: CNN
CNN  — 

Two teams of US scientists have completed lab experiments testing the antibodies from vaccinated and infected Americans to see how well they might be able to fend off currently circulating variants of the virus that causes Covid-19, including the highly mutated BA.2.86.

Their results match up almost exactly, and the news – at least when it comes to BA.2.86, which has also been dubbed Pirola – is very good. Our immune systems can recognize and fight off this variant as well as, and perhaps even a bit better than, the currently circulating offshoots of the XBB variant.

What’s more, people who had the most robust responses against BA.2.86 were those who were within six months of an infection with the XBB subvariant. This suggests that this fall’s updated Covid-19 vaccines, which are designed to fight off XBB.1.5, will provide added protection against a range of circulating Covid-19 lineages, including BA.2.86.

“Two independent labs have basically shown that BA.2.86 essentially is not a further immune escape compared with current variants,” Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center and leader of one of the labs, told CNN.

Their results align with earlier experiments by labs in China and Sweden. Taken together, the data suggests that BA.2.86 will not be as troublesome as experts had feared. In short, this one seems to be a “scariant.”

But another variant, FL.1.5.1, which is causing an estimated 15% of new Covid-19 infections in the US, may be a different story. This fast-growing descendant of the XBB recombinant variant has a constellation of mutations that have raised the eyebrows of variant trackers. In lab testing, it was the most immune-evasive.

“If there wasn’t so much hype about BA.2.86, that would actually be the focus of the paper,” Barouch said.

Concurring findings

Barouch and his team used pseudoviruses: They built the spikes of the BA.2.86 virus and attached them to the body of a different virus. Then they took plasma, the clear part of the blood, from 66 Americans who had been vaccinated with monovalent vaccines only, who had gotten bivalent vaccines or who had recently recovered from an XBB infection, and tested how well their antibodies neutralized 10 Omicron subvariants including BA.2.86.

They found that across a range of different types of immunity, people were able to neutralize BA.2.86 as well as, and sometimes more effectively than, other circulating variants. The people with the highest neutralizing antibodies were those who had recently recovered from an XBB infection.

At the other lab, Dr. David Ho, a professor of microbiology and immunology at Columbia University, and his team used blood plasma from 61 adults: 17 who had gotten three monovalent vaccine doses and two bivalent vaccines, 25 who had recovered from a BA.2 breakthrough infection and 19 who’d recovered from an XBB breakthrough infection.

His results were substantially similar to Barouch’s. Across the range of immune profiles, antibodies in the blood were able to recognize BA.2.86 just as capably as they were other circulating variants. People with the highest degree of immunity against BA.2.86 were those who’d recovered from recent XBB infections.

That was a surprise because of how many mutations BA.2.86 has. Scientists had predicted that based on what was known about those specific mutations, it might be highly immune-evasive.

Barouch said he didn’t believe his first batch of results, so the lab worked all weekend to repeat the experiments. The results were the same.

“It was not exactly what I was expecting,” he said. “Now, they’ve been repeated, and so now we’re confident about them.”

Barouch said he has been asked to brief the White House and the US Centers for Disease Control and Prevention on his findings. “I think these results are pretty important,” he said.

A global effort

Scientists around the world are fast-tracking lab experiments to try to understand the BA.2.86 variant.

Four groups — the two US teams, as well as labs in China and Sweden — have reported results. The early results paint BA.2.86 as more of a paper tiger rather than the looming beast it first appeared to be, although that impression could change as more results come in.

BA.2.86 captured the world’s attention because it looks radically different than any other variants of the coronavirus that we’ve seen so far.

This new lineage has more than 30 changes to its spike protein compared with both its next closest ancestor, BA.2, and with the recently circulating XBB.1.5 lineage. It was an evolutionary leap on par with the one that the original Omicron variant, BA.1, made when it appeared almost two years ago — and everyone remembers how that went down.

During the Omicron wave, infections and hospitalizations hit their highest points of the pandemic in the United States. Weekly deaths reached their second-highest peak, a lesson in how even a tamer version of the virus can be a serious threat if it causes a tidal wave of infection across the population. The vaccines had to be updated.

Omicron quickly overtook other Covid-19 variants and began creating its own offshoots, viruses that we’re still dealing with. It became a lesson in how agile the virus can be and how fragile our defenses are in the face of such large shifts.

Not the ‘second coming of Omicron’

The White House was worried enough about another Omicron-level event that it quietly polled about a dozen experts earlier this year about the chances the world would see one within the next two years. Most experts pegged the possibility between 10% and 20%.