Here’s What We Know About Omicron XE — The New Covid Variant Found In The U.K.

Topline

A new Covid-19 variant that combines two different omicron strains has been identified in the United Kingdom, and it could be the fastest-spreading Covid variant yet, according to early data from British public health officials and the World Health Organization, though experts warn it is too soon to determine if or how much of a threat the variant might be.

A new recombinant variant of Covid was found in England.

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Key Facts

The variant, called XE, was first detected in England in mid-January, according to the U.K. Health Security Agency (UKHSA), and has been confirmed in more than 600 cases in England since, less than 1% of virus samples analyzed during that time.

As of March 22, 763 samples of XE had been identified in the U.K., and a very limited number of cases have reportedly been found in China and Thailand.

XE is a recombinant virus—effectively a combination of genetic material from two or more different viruses—containing elements of the original omicron strain, BA.1, and the more infectious BA.2 subvariant, also known as “stealth omicron.”

Early data from the UKHSA and WHO suggests the XE variant could be around 10% more transmissible than the BA.2 omicron subvariant, already the most contagious Covid variant and one of the most contagious diseases in human history.

Susan Hopkins, chief medical adviser for UKHSA, said more data will be needed to confirm whether XE has a “true growth advantage,” as it has shown a “variable growth rate” so far over the time it has been monitored.

There is also insufficient evidence to draw any conclusion on transmissibility, severity or vaccine effectiveness, Hopkins said, adding that the UKHSA will continue to monitor the situation “closely.”

Key Background

It is normal and expected that viruses will change over time. Many of these changes are the result of genetic mutation but some major changes can come about when a person is infected with more than one type of virus. When this happens, viruses can exchange and swap parts of their genetic makeup as they replicate inside our cells, effectively creating a hybrid with elements of both “parents.” Recombinant viruses are “not an unusual occurrence,” Hopkins said, “particularly when there are several variants in circulation.” A number of Covid recombinants have been identified during the pandemic, she noted, and most “die off relatively quickly” as with other variants.

What We Don’t Know

How a new variant will affect Covid treatments. New variants can possibly evade existing vaccines and treatments for Covid-19. Omicron is better able to avoid the protection offered by vaccination and previous infection, for example, and both BA.1 and BA.2 are resistant to most monoclonal antibody treatments. AstraZeneca’s treatment, Evushield, still appears to work against the variants, as do antiviral drugs paxlovid and molnupiravir. There is no data yet on whether XE is able to evade these treatments.

What To Watch For

A new named variant. The WHO assigns Greek letter names like alpha, delta and omicron to variants of particular concern or interest. It does so based on significant behavioral differences between variants, not just genetic differences. Two omicron subvariants—BA.1 and BA.2—are still classified as omicron despite being about as genetically distinct as earlier variants alpha, beta and gamma were from one another. The WHO said it will classify XE under the omicron umbrella until “significant differences in transmission and disease characteristics, including severity, may be reported.” These differences have not been reported so far.

Tangent

The UKHSA said it is also monitoring two other Covid recombinants: XD and XF. Both variants are a genetic mix of delta and omicron BA.1. Only 38 cases of XF have been identified in the U.K. since mid-February and no cases of XD. Just 49 cases of XD have been reported to global databases, the UKHSA said. The majority of these were found in France.

Surprising Fact

Coronaviruses have been known to recombine with other types of virus, including influenza and rotaviruses. While potentially unlikely due to the rarity of successful recombinants, it’s plausible a variant could emerge from a combination of SARS-CoV-2, the virus behind Covid, and another virus. Such a recombinant could have new and unexpected properties