COVID-19 subvariant XE: What to knowThe Honorable Robert Redfield, M.D.
It’s nicknamed Frankenstein, but experts say that shouldn’t scare you.
The World Health Organization (WHO) recently issued a preliminary report on the new COVID-19 “Frankenstein” subvariant called XE, which is a mix of the omicron BA.1 variant and the “stealth” variant BA.2, with the agency declaring it’s still part of the omicron variant, but not a variant of interest or concern yet, according to a recent Euronews report.
The XE strain was first detected in the United Kingdom on January 19, with now over 1,000 cases spreading by community transmission, with the majority in the east of England, London, and South East London, per the report.
A “recombinant” strain is a type of variant that occurs when an individual becomes infected with two or more variants at the same time, and are assigned the letter “X” prefix to classify them as recombinant, said Dr. Stacia Wyman, senior genomics scientist at the Innovative Genomics Institute at UC Berkeley.
Wyman noted the XE subvariant originated from someone who was infected with both the BA.1 and BA.2 variants.
“When the virus was replicating, there was an error and the two viruses combined,” she said. “Then the combined virus replicates and is spread to other people.”
XE’s genomic sequence is part BA.1 and part BA.2, but the gene that codes for the spike protein that helps the virus attach to healthy cells comes from BA.2. But even though it’s part BA.2, it’s still unknown if previous BA.2 infection will provide immunity to XE, Wyman said.
“Early-day estimates indicate a community growth rate advantage of ~10% [for XE] as compared to BA.2, however this finding requires further confirmation,” the WHO said.
But the UK Health Security Agency (UKHSA) noted: “There is currently insufficient evidence to draw conclusions about growth advantage or other properties of this variant,” according to a March 25 updated release.
People are testing positive for 10 days or more when they are diagnosed with the XE variant, said Denis Kinane, immunologist and founding scientist of United Kingdom-based Cignpost Diagnostics.
“Our current data is showing that many people are testing positive for 10 days or more rather than the 6 or 7 days we saw by frequent testing at the beginning of the omicron wave, which means the virus has more opportunity to spread more widely and this may be BA-2 and XE’s transmissibility advantage,” Kinane said.
At least two XE cases have been sequenced in Wisconsin and one in New York with also two unconfirmed cases in California, according to Wyman. Japan, China, Thailand, India, New Zealand, and Israel have reported COVID-19 cases secondary to the XE subvariant, in addition to the U.K.
“We continue to monitor cases of the recombinant XE variant in the U.K., which currently represents a very small proportion of cases,” said Meera Chand, director of clinical and emerging infections at UKHSA.
“Recombinant variants are not unusual, particularly when there are multiple variants in circulation – and several have already been identified over the course of the pandemic,” said Dr. George Thompson, professor of medicine at the University of California, Davis, School of Medicine in the Division of Infectious Diseases.
Thompson told Fox News: “It may be slightly more transmissible than the parent variant but it is too early to known if outcomes differ from other COVID variants.”
“As with other kinds of variant[s], most will die off relatively quickly,” said Susan Hopkins, chief medical advisor of UKHSA.
Because viruses naturally mutate over time, recombinant strains are not surprising, so presently XE does not appear to be more effective at evading immunity from previous vaccination or prior COVID-19 infection compared with the previous strains, said Dr. Carlos Malvestutto, an infectious disease specialist at the Ohio State University Wexner Medical Center.
But Hopkins noted, “So far there is not enough evidence to draw conclusions about transmissibility, severity or vaccine effectiveness.”
Some experts argue, however, because XE is a combined strain of both BA.1 and BA.2 and vaccination protects against symptomatic disease for BA.1 and BA.2 strains, it is likely vaccination will also protect against symptomatic disease caused by XE, said Dr. Andrew Badley, professor of infectious disease at the Mayo Clinic and chair of the COVID-19 Task Force for Mayo Clinic.
The most common symptoms reported of the XE strain are similar to the cold-like symptoms of original strain of omicron – especially in vaccinated people, like runny noses, sore throats and sneezing in contrast to the original strain of the virus that causes COVID-19, like fevers, cough or loss of taste or smell, according to the Independent.
Badley added: “We also know that the other therapies that are being used particularly in the outpatient setting—Paxlovid and molnupiravir—should, based on how they work, have continued activity against the XE strain.”
But Badley noted because some monoclonal antibody therapies are not effective against BA.1 and BA.2, it is likely those specific antibody treatments won’t work against XE either.
“The key takeaway is that for each of these variants and subvariants, risk of hospitalization and death appears to be, on average, lower where vaccination rates are higher, indicating that vaccination, including a third dose, should be effective in reducing risk for severe disease,” said Stephanie Silvera, professor of public health at Montclair State University.
Approximately 62% of all COVID-19 cases in the United States are currently BA.2, but a new BA.2 subvariant, BA.2.12.1, is now responsible for 36.5% of new coronavirus infections, according to recent data from the Centers for Disease Control and Prevention (CDC).
“We’re just starting to learn about the impact of BA.2.12.1,” CDC Director Rochelle Walensky said.
“It appears it might have a transmission advantage of about 25% over the BA.2 subvariant. … But importantly, we continue to believe that those who are vaccinated and especially those who are boosted, continue to have strong protection against severe disease, even from BA.2.12.1.”
Wyman added the XE recombinant strain “may die out completely regionally and never spread.”
“It’s something to keep an eye on, but not for the general population to worry about.”