BA.2 ‘stealth Omicron’ subvariant could be severe – University of Tokyo

The BA.2 virus, a subvariant of Omicron, may cause more severe disease and appears capable of thwarting some of the key weapons we currently have against Covid-19.

There is mixed evidence concerning research into Omicron’s distant cousin, but a Japanese study shows it could be as severe as Delta.

Omicron BA.2 variant

Resistant to treatments

According to a CNN report, new lab experiments from Japan show BA.2 may cause serious illness similar to older variants of Covid-19, including Delta.

Like Omicron, it also appears to largely escape the immunity created by vaccines. A booster shot restores protection, making illness after infection about 74% less likely.

BA.2 also appears resistant to some treatments, including sotrovimab, the monoclonal antibody that’s currently being used against Omicron.

BA.2 ‘stealth Omicron’

The findings were posted Wednesday as a preprint study on the bioRxiv server, before peer review.

“It might be, from a human’s perspective, a worse virus than BA.1 and might be able to transmit better and cause worse disease,” says Dr Daniel Rhoads, section head of microbiology at the Cleveland Clinic in Ohio.

A University of Tokyo researcher ad the person who conducted the study, Kei Sato argued these findings prove that BA.2 should not be considered a type of Omicron and that it needs to be more closely monitored.

“As you may know, BA.2 is called ‘stealth Omicron’,” Sato told CNN. That’s because it doesn’t show up on PCR tests as an S-gene target failure, the way Omicron does.

“Labs, therefore, have to take an extra step and sequence the virus to find this variant,” said Sato.

Mixed real-world data

According to the World Health Organization (WHO), the BA.2 variant has been estimated to be about 30% more contagious than Omicron.

So far, it’s been detected in 74 countries and 47 states in the USA.

The US Centers for Disease Control and Prevention estimates 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.

The subvariant has become dominant in at least 10 other countries including Bangladesh, Brunei, China, Denmark, Guam, India, Montenegro, Nepal, Pakistan and the Philippines, as per the WHO’s weekly epidemiological report.

However, there’s mixed evidence on the BA.2’s severity as hospitalisations continue to decline in countries South Africa and the United Kingdom.

But in Denmark, BA.2 is the leading cause of infections and hospitalisations, and deaths continue to rise.

Monoclonal antibody treatments

The new study found that BA.2 can copy itself in cells more quickly than the original version of Omicron.

It’s also more adept at causing cells to stick together. This allows the virus to create larger clumps of cells, called syncytia.

That’s concerning because these clumps then become factories for churning out more copies of the virus.

Delta was also good at creating syncytia, which is thought to be one reason it was so destructive to the lungs.

Similar to Omicron, the BA.2 subvariant was capable of breaking through antibodies in the blood of people who’d been vaccinated against Covid-19.

It was also resistant to the antibodies of people who’d 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.

Experts have also warned countries against lifting mask mandates.

Compiled by Narissa Subramoney

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