And like Omicron, it seems to largely escape the immunity created by vaccines. A booster shot restores protection, making illness after infection about 74% less likely.
BA.2 is also resistant to certain treatments, including sotrovimab, the monoclonal antibody currently used against Omicron.
“It could be, from a human point of view, a worse virus than BA.1 and could be able to transmit itself better and cause more serious disease,” says Dr Daniel Rhoads, head of the microbiology section. at the Cleveland Clinic in Ohio. Rhoads reviewed the study but was not involved in the research.
The US Centers for Disease Control and Prevention is watching BA.2 closely, its director, Dr. Rochelle Walensky, said.
“There is no evidence that the BA.2 lineage is more severe than the BA.1 lineage. The CDC continues to monitor variants that are circulating both domestically and internationally,” she said Friday. . “We will continue to monitor emerging data on the severity of disease in humans and the results of articles like this made in the laboratory.”
BA.2 is highly mutated from the original Covid-causing virus that emerged in Wuhan, China. It also exhibits dozens of different genetic changes from the original Omicron strain, making it as distinct from the most recent pandemic virus as the Alpha, Beta, Gamma, and Delta variants were from each other.
Kei Sato, a researcher at the University of Tokyo who conducted the study, says these results prove that BA.2 should not be considered a type of Omicron and should be watched more closely.
“As you may know, BA.2 is called ‘Omicron Stealth,'” Sato told CNN. This is because it does not show up on PCR tests as an S gene target failure, as Omicron does. So labs have to go the extra step and sequence the virus to find this variant.
“Establishing a method to specifically detect BA.2 would be the first thing” many countries need to do, he says.
“It looks like we could be looking at a new Greek letter here,” agreed Deborah Fuller, a virologist at the University of Washington School of Medicine, who reviewed the study but was not part of the research.
Mixed real-world data on sub-variant severity
BA.2 has been estimated to be about 30% more contagious than Omicron, according to the World Health Organization. It has been detected in 74 countries and 47 US states.
The US Centers for Disease Control and Prevention estimates that about 4% of Americans with Covid-19 now have infections caused by BA.2, but many other parts of the world have more experience with this variant. It has become dominant in at least 10 other countries: Bangladesh, Brunei, China, Denmark, Guam, India, Montenegro, Nepal, Pakistan and the Philippines, according to the World Health Organization’s weekly epidemiological report.
However, there is mixed evidence on the seriousness of BA.2 in the real world. Hospitalizations continue to fall in countries where BA.2 has gained a foothold, such as South Africa and the United Kingdom. But in Denmark, where BA.2 has become the leading cause of infections, hospitalizations and deaths are on the rise, according to the WHO.
Resistant to monoclonal antibody treatments
The new study found that BA.2 can copy itself into cells faster than BA.1, the original version of Omicron. It is also better able to make cells adhere. This allows the virus to create larger clumps of cells, called syncytia, than BA.1. This is worrying because these clumps then become factories to produce more copies of the virus. Delta was also good at creating syncytia, which would be one of the reasons it was so destructive to the lungs.
When the researchers infected hamsters with BA.2 and BA.1, animals infected with BA.2 became sicker and had worse lung function. In tissue samples, the lungs of hamsters infected with BA.2 showed more damage than those infected with BA.1.
Similar to the original Omicron, BA.2 was able to break down antibodies in the blood of people vaccinated against Covid-19. It was also resistant to antibodies from people who had been infected with Covid-19 early in the pandemic, including Alpha and Delta. And BA.2 was almost completely resistant to some monoclonal antibody treatments.
But there was a silver lining: Antibodies in the blood of people who had recently had Omicron also appeared to have some protection against BA.2, especially if they had also been vaccinated.
And that brings up an important point, says Fuller. Even though BA.2 appears more contagious and pathogenic than Omicron, it may not cause a more devastating wave of Covid-19 infections.
“One of the caveats that we have to think about when we get new variants that might seem more dangerous is the fact that there are two sides to the story,” says Fuller.
The virus is important, she says, but as its potential hosts, so are we.
“Our immune system is also evolving. And so that pushes things back,” she said.
Right now, she says, we are in a race against the virus, and the key question is who is in the lead?
“What we’ll ultimately want is for the host to be ahead of the virus. In other words, our immunity, to be one step ahead of the next variant that comes out, and I don’t know if we we’re still here,” she said.
For that reason, Fuller says, she feels it’s not quite time for communities to lift mask mandates.
“Before this thing came out, we were about 10 feet from the finish line,” she said. “Taking the masks off now is not a good idea. It will just prolong it. Let’s go to the finish line.”