New Covid Variant: What We Know About the BA.2 Omicron Strain
At least 40 countries, including Denmark, India and the U.K., have detected the variant
The BA.2 variant has been detected in the U.S., according to the CDC. A Covid-19 testing site in Whittier, Calif.
As newly reported cases of Covid-19 decline in parts of the U.S., researchers around the world are monitoring a new variant of the Omicron variant dubbed BA.2. The variant is under observation by countries including Denmark, India and the U.K., though little is still known about its properties and the threat it may pose.
Here’s what scientists and public-health experts know so far about the BA.2 variant:
What is the BA.2 variant of Covid-19?
The BA.2 variant of Covid-19 is a relation of the widely-spreading original Omicron variant known as BA.1, according to Theodora Hatziioannou, an associate professor of virology at Rockefeller University.The two variants arose around the same time and come from the same ancestor strain. They have many mutations in common but there are also around 20 mutations that are different between the two variants. The differences between this variant and BA.1 can be seen in the spike protein of the virus, Dr. Hatziioannou said.
This was the first time that two competing variants emerged in parallel like this, according to Mark Zeller, a genomic epidemiologist at the Scripps Research Institute in San Diego, Calif. He said he expected BA.2 to drive another rise in cases, but not at the same rate that BA.1 did, because people who were infected with the original Omicron strain likely have some immunity to BA.2.
Viruses mutate all the time and diversification within a variant is normal. The earlier Delta variant comprised more than 200 sublineages before it was replaced by Omicron, according to Francois Balloux, director of the University College London Genetics Institute.
Is the BA.2 variant in the U.S.?
Yes. The BA.2 variant has been detected in the U.S., according to the Centers for Disease Control and Prevention, which provides estimates of the prevalence of various Covid-19 strains. The CDC’s estimates show that Omicron was likely responsible for 99.9% of Covid-19 infections in the week ending Jan. 22. The CDC said the prevalence of some other variants including BA.2 was included in the Omicron tally.Where else in the world has the BA.2 variant been detected?
At least 40 countries have detected the BA.2 variant, including the U.K., Denmark, India, Sweden, Singapore and the Philippines. It isn’t possible at this point to determine where the sublineage originated, according to the U.K. Health Security Agency.The BA.2 variant may be displacing the BA.1 in Denmark, said Dr. Hatziioannou. “They’re identifying more and more cases of BA.2 rather than BA.1,” she said.
Is BA.2 a Covid-19 variant of concern?
No. The World Health Organization designated Omicron the fifth “variant of concern” in November based on the risks posed by changes in its makeup and behavior compared with other versions of the virus, including its increased infectiousness. It hasn’t given BA.2 any designation but has urged researchers to closely track and study the variant. Earlier variants of concern included Delta, which drove a wave of cases in the U.S. and elsewhere last summer, and Beta, which like Omicron was first identified in South Africa.Other variants have remained variants of interest, meaning they have genetic changes that affect the way the virus works, according to the WHO. Lambda and Mu are variants of interest that sickened people in some parts of the world, such as South America, but didn’t outcompete variants including Delta in the U.S. and elsewhere.
What are the symptoms for the BA.2 variant? Is the BA.2 variant more severe than the Omicron variant?
It isn’t clear whether the BA.2 variant behaves in materially different ways than the Omicron variant, which research has shown to be far more infectious than previous strains but also less likely to lead to severe disease in many cases.
In Denmark, one of the countries with high rates of BA.2, an initial analysis by the government-run State Serum Institute showed no differences in hospitalizations for BA.2 compared with BA.1.
The Serum Institute reported on Jan. 27 that “preliminary calculations indicate that BA.2 is effectively well over one and a half times more contagious than BA.1.”
Though BA.2 continues to spread in different countries, the CDC said the variant was responsible for a very small share of recent Covid-19 infections compared with other circulating viruses in the U.S. and around the world. “Currently 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,” said the agency.
How is the BA.2 variant responding to treatment and vaccinations?
Though it is too early to tell, Dr. Hatziioannou predicts the BA.2 variant will be as resistant to monoclonal antibodies as BA.1. She said there are only slight differences on the spike protein of BA.2 compared with BA.1, leading her to conclude that they are likely to behave similarly. The monoclonal antibody treatment made by GlaxoSmithKline PLC may be effective in treating this variant because it has been successful in treating BA.1. Pfizer Inc. and Merck & Co. and its partner Ridgeback Biotherapeutics LP developed antiviral pills for Covid-19 that continue to work against the original Omicron variant and may have similar effects against BA.2.Researchers predict that there won’t be a significant difference in how vaccines hold up against BA.2, compared with the original Omicron. Most of the mutation differences between the two variants occur outside areas of the virus that are important for immune recognition. An analysis by the U.K. Health Security Agency found similar vaccine effectiveness against symptomatic disease from both BA.1 and BA.2. Further studies are under way.
“I can be pretty confident in saying that vaccines will continue to work really well at keeping people away from the hospital if they are boosted,” said Peter Chin-Hong, infectious disease specialist at the University of California, San Francisco. When fully vaccinated and boosted, your cells adopt memory and are able to detect similar variants, preventing you from getting extremely sick if infected, Dr. Chin-Hong said.
