- The omicron subvariant, known as BA.2, is 1.5 times more transmissible than the original omicron strain, according to Danish scientists.
- The U.K. Health Security Agency on Friday said BA.2 has a "substantial" growth advantage over the original omicron, known as BA.1.
- Nearly half of U.S. states have confirmed the presence of BA.2 with at least 127 known cases nationwide as of Friday.
There are already dozens of cases across almost half of the U.S. of a new Covid subvariant that's even more contagious than the already highly transmissible omicron variant.
Nearly half of U.S. states have confirmed the presence of BA.2 with at least 127 known cases nationwide as of Friday, according to a global data base that tracks Covid variants. The Centers for Disease Control and Prevention, in a statement Friday, said although BA.2 has increased in proportion to the original omicron strain in some countries, it is currently circulating at a low level in the U.S.
The subvariant is 1.5 times more transmissible than the original omicron strain, referred to by scientists as BA.1, according to Statens Serum Institut, which conducts infectious disease surveillance for Denmark.
The new sublineage doesn't appear to further reduce the effectiveness of vaccines against symptomatic infection, according to the U.K. Health Security Agency.
"Currently there is no evidence that the BA.2 lineage is more severe than the BA.1 lineage," CDC spokesperson Kristen Nordlund said.
BA.2 overtook the original omicron as the dominant variant in Denmark over the course of a few weeks, said Troels Lillebaek, the chairman of the Scandinavian nation's committee that conducts surveillance of Covid variants.
BA.1 and BA.2 have many differences in their mutations in the most important areas. In fact, the difference between BA.1 and BA.2 is greater than the difference between the original "wild strain" and the Alpha variant, which was the first major mutation to take root across the world.
The BA.2 variant has five unique mutations on a key part of the spike protein the virus uses to attach to human cells and invade them, Lillebaek told CNBC. Mutations on this part of the spike, known as the receptor binding domain, are often associated with higher transmissibility.
The U.K. Health Security Agency on Friday said BA.2 has a "substantial" growth advantage over the original omicron. The sister variant spread faster than the original omicron in all regions of England where there were enough cases to conduct an analysis, according to the agency.
However, a preliminary assessment found that BA.2 doesn't appear to reduce the effectiveness of vaccines any more than the original omicron. A booster dose was 70% effective at preventing symptomatic illness from BA.2 two weeks after receiving the shot, compared with 63% effectiveness for the original omicron strain.
The World Health Organization has not labeled BA.2 a separate variant of concern from omicron. However, WHO officials have repeatedly warned that new variants will arise as omicron spreads across the world at an unprecedented rate. Maria Van Kerkhove, the WHO's Covid-19 technical lead, warned on Tuesday that the next Covid will variant be more transmissible.
"The next variant of concern will be more fit, and what we mean by that is it will be more transmissible because it will have to overtake what is currently circulating," Van Kerkhove said. "The big question is whether or not future variants will be more or less severe."
Lillebaek said there is not enough data yet to determine whether BA.2 is able to reinfect people who caught the original omicron. However, prior infection would likely provide some crossover immunity to BA.2.
New Covid cases are increasing in Denmark, with more than 50,000 new infections reported on Friday in a country of 5.8 million people, according to the country's health ministry. Lillebaek said it's safe to assume that BA.2 is driving the increase of new infections in Denmark right now.
New hospital admissions in Denmark rose by 12 for a total of 967 patients who are Covid positive. Lillebaek said this increase is likely within the limits of what the health system can manage. However, he noted that 80% of Danes are fully vaccinated and 60% have received booster shots.
"If you are in a community or living in a country where you have a low vaccination rate, then you will have for sure more admissions to hospital and more severe cases and then more going to ICU," he said.
In the U.S., about 67% of those eligible are fully vaccinated, according to data from the CDC.