Though COVID-19 cases and deaths continue to fall worldwide, medical experts and public health agencies continue to identify new variants of the virus.
BA.2, a subvariant of omicron that experts believe is more contagious than the original BA.1, became dominant in the U.S. in late March.
More recently, some people have expressed concerns online about a potential new coronavirus variant called XE, with one Twitter user claiming that it was found in the United Kingdom and “could be the most transmissible variant yet.” Another person said XE combines BA.1, the original version of omicron, and omicron subvariant BA.2.
Is there a new coronavirus subvariant called XE?
- The World Health Organization (WHO)
- Centers for Disease Control and Prevention (CDC)
- United Kingdom Health Security Agency
- Saralyn Mark, M.D., former senior medical advisor to the White House and American Medical Women's Association COVID-19 Lead
Yes, there is a new coronavirus subvariant called XE. It combines the BA.1 and BA.2 versions of omicron.
WHAT WE FOUND
Viruses like the one that causes COVID-19 mutate as they replicate. People can be infected with different strains of a virus at the same time and sometimes they combine during replication, Saralyn Mark, M.D., former senior medical advisor to the White House and American Medical Women's Association COVID-19 Lead, explained.
In its weekly epidemiological update released on March 29, the World Health Organization (WHO) said XE is a recombinant variant, or combination, of the BA.1 and BA.2 versions of omicron. It was first detected in the United Kingdom on Jan. 19.
The United Kingdom Health Security Agency (UKHSA) said in an update on March 25 that 637 cases of XE had been confirmed in the country so far. During the first week of April, more than 333,000 people total had tested positive for COVID-19 in the UK, the agency reported on April 8.
A “small number” of XE cases have been detected in the US, where the new subvariant is considered “another lineage of omicron and not a new variant of interest or concern,” a spokesperson for the Centers for Disease Control and Prevention (CDC) told VERIFY.
Is XE more contagious than other COVID-19 strains?
Early data show the XE subvariant may be about 10% more transmissible than BA.2, but it’s too early to know exactly how contagious it is, the WHO and other experts say. According to UKHSA, the data “cannot yet be interpreted as an estimate of growth advantage” for the XE subvariant.
If XE is 10% more transmissible than BA.2, that would make it “one of the most transmissible viruses in the world,” Mark said.
Medical experts don’t have enough evidence yet to draw conclusions about severity or vaccine effectiveness either. But the CDC expects the XE subvariant to behave similarly to BA.2 because they share the same spike protein.
Some medical experts believe BA.2 is about 50% more contagious than BA.1. But vaccines provide the same level of protection against severe illness and hospitalization of BA.2 compared to other variants.
How common are recombinant variants?
Recombinant variants “are not an unusual occurrence, particularly when there are several variants in circulation, and several have been identified over the course of the pandemic to date,” Professor Susan Hopkins, chief medical advisor with UKHSA, said.
Another recombinant variant identified during the pandemic is a combination of the delta and omicron variants that some have called “deltacron.” Delta-omicron recombinant cases are “exceedingly rare” in the United States, the CDC previously told VERIFY.
Most recombinant variants “die off relatively quickly,” Hopkins said. It’s unclear right now if this will happen with the XE subvariant.
Though immunity to BA.1 and BA.2 currently remains high due to COVID-19 vaccines and natural infection, it could wane over time and allow a new subvariant like XE to take hold in the US, Mark said.