What's a Subvariant? What You Should Know About Omicron BA.2

A new version of the Omicron variant is spreading in many countries across the world, according to the World Health Organization (WHO). The organization recommended researchers begin investigating whether the latest version behaves differently from Omicron and if it poses new challenges or threats to the current state of the pandemic. 

The new strain of the virus is known as BA.2, and it’s a subvariant of Omicron (also known as BA.1, according to virologists). The WHO reports that BA.2 is different from Omicron because it has variations in some of its mutations, including ones in the spike protein of the virus.

As of right now, health experts and researchers don’t know much about the new subvariant.

“It’s kind of a mystery upon a mystery at this point,” Jeremy Luban, MD, a professor of molecular medicine, biochemistry, and molecular pharmacology at University of Massachusetts Medical School, told Verywell. “We don’t know where BA.2 even came from or where Omicron came from, there’s a lot of good ideas about it, but the fact is we don’t know.”

Here’s everything we know so far about the new strain, including where it is now and if health experts think it’s a cause for concern.

What Do We Know About BA.2 Right Now? 

BA.2 is currently present in many countries. According to Denmark’s governmental research institute, Statens Serum Institut, BA.2 accounted for almost half of all Danish Omicron cases.

“Last week in Denmark, BA.2 was about 60% of the cases, they also have BA.1 but it looks like BA.2 is replacing BA.1,” Luban said. “We’re also seeing presence at high levels in certain locations including several countries in Asia.”

BA.2 was designated a variant under investigation by the UK Health Security Agency on January 21, 2022, due to an increasing number of cases identified both domestically and internationally. And Luban said while BA.2 is most prominent in Denmark right now, the variant is popping up in India, Sweden, and Singapore. The subvariant is also being reported in the United States including in Washington state, Texas, New Mexico, and California.

“We’re just starting to detect it, the first sequences are just coming in. They are low numbers, but it’s here,” Luban said. “You can see the numbers are going up, they’re small but as we saw with Omicron BA.1, that can change very quickly.”

Daniel Kuritzkes, MD, professor at Harvard Medical School and chief of the division of infectious diseases at Brigham and Women’s Hospital, told Verywell while it’s not known when or where BA.2 first emerged, it’s an offshoot of the original Omicron variant that emerged a few months ago. 

“BA.1 and BA.2 were detected at a similar time frame, all arising from the same ancestral virus,” Kuritzkes said. “Why BA.2 is now becoming more frequent in some countries than BA.1 is not known and whether it would take off in the way that the original Omicron did is hard to predict at this time.” 

Why Is BA.2 Considered a Subvariant?

BA.2 is a descendant of the original Omicron variant. Since BA.2 shares a common lineage to BA.1, it is currently considered a subvariant, according to Luban.

Other experts support this, including Sri Banerjee, MD, PhD, a faculty member in Walden University’s PhD in Public Health Program, who told Verywell in an email it’s about the similarities in the genetic makeup of BA.1 and BA.2.

“BA.2 has 32 mutations in common with BA.1, making BA.2 a subvariant and not a new variant,” Banerjee said. “BA.2 is widely considered stealthier than the original version of Omicron because particular genetic traits make it somewhat harder to detect.” 

However, BA.2 could be designated as a distinct variant to distinguish it from Omicron if it continues to spread and infect people in high numbers.

“BA.1 and BA.2 are lumped together in this Omicron category, but I believe that if BA.2 takes off in the way it looks like it is doing right now, it’s probably going to acquire its own name,” Luban said. “We may have a new Greek letter for it.”

How Different Is BA.2 From the Original Omicron Variant? 

According to the WHO, while Omicron and BA.2 are considered closer to each other than other viruses (such as Alpha, Delta, and Gamma), they are still different from each other in important ways. There are differences in some mutations, including in the spike protein, which affects how easily strains can be differentiated.

Kuritzkes stated BA.2 shares many but not all mutations that are seen in Omicron. While the new subvariant has unique mutations compared to the original variant, how efficiently it enters cells, or how it neutralizes antibodies and vaccines are still being explored at this time.

“BA.2 has a number of mutations that BA.1 does not have that are in the region of genomes that concerns us,” Luban said. “It’s like when Omicron first hit. In the first few days, we had a sequence, the sequence itself was terrifying, but it took time before we could find out if Omicron would be more pathogenic and infectious.” 

How Transmissible Is It? 

Based on recent data from Denmark, the subvariant has spread rapidly. Health officials say more information is needed at this time before determining the transmissibility of BA.2. 

“BA.2 is 1.5 times more infectious than the original Omicron but does not seem to be causing an increase in hospitalizations in Denmark,” Banerjee said. “However, the higher transmissibility is being monitored as we still have too little information at this time."

It’s also still unclear if the new version spreads faster than BA.1 or if it causes more severe symptoms.

“Questions of how infectious it is compared to what’s out there, how severe is the illness, and what cross-protection do we see from the vaccines will take time to answer,” Kuritzkes said. “You need an accumulation of cases to see how rapidly the variant is spreading, which we don’t have right now.”

While researchers are still learning more about the new subvariant, experts don’t want people to panic. Viruses mutate constantly, mostly in harmless ways, added Banerjee. Other experts stress that there is no evidence to suggest that BA.2 is more harmful than Omicron.

“Anytime something changes, it’s a reason for concern until we know more about it,” Luban said. “There is a large body of data that indicates if you’ve been vaccinated, you’re likely to be protected from severe disease or death against any of the viruses we’ve seen so far.”

While we don’t yet know if the vaccines can protect against this new subvariant, researchers say because the subvariant’s genetic sequence is similar to Omicron, vaccines can offer some protection against BA.2.

“It’s absolutely clear that vaccines protect you from severe disease against Omicron and the other variants we’ve seen, so there’s no reason to think the same wouldn’t be true for this new variant, BA.2,” Luban said.

Its safe to assume, for now, that vaccination will likely offer protection against the subvariant.

“Until we see laboratory data on how neutralizing BA.2 is with antibodies induced by the vaccine, we don’t formally know,” Kuritzkes added. “But since we know that the vaccine protects against severe disease with BA.1 and offers some protection against becoming infected, similar protection should be expected against BA.2.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

Correction - January 31, 2022: A previous version of this article misquoted Sri Banerjee. It has been updated to reflect a correction in BA.2’s impact on hospitalizations in Denmark.