What to Know About the Omicron XE Variant

A new COVID-19 variant has been identified in the United Kingdom. The recombinant variant, dubbed XE, is a hybrid of Omicron BA.1 and BA.2.

XE was first detected in the U.K. on January 19. Since then, the U.K. health ministry has reported more than 630 cases of the variant, less than 1% of the country’s millions of COVID-19 cases.

Early estimates indicate the variant is 10% more transmissible than BA.2. In its weekly epidemiological update last week, the World Health Organization (WHO) cautioned that this estimate is preliminary, and the organization is monitoring the variant.

But health authorities said the new variant is not yet a cause for concern.

“XE has shown a variable growth rate and we cannot yet confirm whether it has a true growth advantage,” Susan Hopkins, chief medical advisor to the U.K. Health Security Agency, said in a statement. “So far there is not enough evidence to draw conclusions about transmissibility, severity or vaccine effectiveness.”

In March, researchers also reported cases of a new variant that combined characteristics of Delta and Omicron. The WHO said that as of March 29 there has been no new evidence to indicate that this recombinant variant poses a public health risk.

What Is a Recombinant Virus?

Recombinant viruses arise when two or more strains swap some of their genetic material. A new hybrid virus is born, which typically contains some characteristics of each of the strains.

This process happens naturally in coronaviruses and some other viruses. Though recombination is expected, it’s not very common—up to 5% of circulating COVID-19 cases in the U.S. and U.K. may be recombinants, according to an analysis that has not yet been peer-reviewed.

“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. As with other kinds of variant, most will die off relatively quickly,” Hopkins said.

When new recombinant variants are designated, scientists give them a name that starts with an “X” and is followed by a letter, depending on the order of their discovery. XE will be considered an Omicron variant unless the variant shows significantly different disease characteristics.   

If XE continues to spread, scientists may perform more studies to assess its infectiousness and ability to make people sick.

BA.2 overtook BA.1 to become the dominant COVID-19 strain the U.S. last week, and both subvariants are circulating nationwide. No cases of a BA.1 and BA.2 recombinant have yet been reported in the U.S.

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.