Daughter of Omicron BA.1 and BA.2 may be more transmissible but does not currently appear to cause more serious disease. The “hybrids” will be more and more frequent
What is XE?
We have been talking about it for days: the new hybrid variant of Covid 19, baptized XE is arousing new concerns
just at a time when almost the whole world is abandoning the restrictions, including Italy. XE is one combination of already highly transmissible variants BA.1 and BA.2 from Omicron and was first detected on January 19th in the UK. XE has three mutations that are not present in either BA.1 or BA.2. His proteina Spike deriva and BA.2which in Italy had reached a prevalence of 44 percent as early as last March 22.
According to some scientists anyone infected with BA.2 should retain some protection against XE (the swab, however, only detects the positivity and not the strain), although for now it is still very preliminary hypotheses.
“Recombinant variants are well described for other viruses and are often not associated with greater danger,” says Dr. Andrew Badley, Professor of Infectious Diseases at the Mayo Clinic.
How widespread is XE?
Globally they have been awarded so far 700 XE viral genomes (637 in the United Kingdom, where the variant was detected thanks also to the efficiency of the laboratories, 49 in the USA and other cases in Thailand, India, Japan). According to the English report, the XE variant would appear more frequent in women in all age groups.
Is it really more transmissible?
According to current estimates they come from the UK XE has a transmission advantage ranging from 12.6% to 20.9% over Omicron 2
and this would make it the most transmissible sub-variant of Omicron to date. Whenever a new, more transmissible variant emerges, it is highly likely that it will become dominant over time. However, the available data do not allow conclusions to be drawn on this point. However, if the transmissibility data were confirmed, some estimates go so far as to state that in the United Kingdom XE could become dominant within a couple of months.
Is this a disturbing variant?
The World Health Organizationà did not assign a Greek letter to XE: belongs to Omicron for the time being, at least until significant differences in transmission and disease characteristics, including severity, are identified. Has not been classified as a new VOC (variant of concern)
What kind of disease does it cause?
There are no statistically relevant data on its severity (although the mortality or hospitalization rate does not seem to have changed) or on the ability to evade immunity acquired from vaccine or from previous contagion. So far there have been no reports of different symptoms including fatigue, lethargy, fever, headache, muscle and bone pain. However at present the severity of XE disease appears to be mild and there would be no difference with Omicronalthough it must be taken into account that more and more people, globally, are vaccinated, and that this can contribute to a manifestation of milder symptoms.
How do hybrid variants emerge?
Each individual virus is typically an almost exact copy of its only parent. However viruses can undergo a process called recombination and have two parents. THE Recombinant viruses can emerge when two or more variants infect the same cell in an individual, allowing variants to interact during replication. This mechanism involves a “Mixture” of genetic material and thus new combinations of viruses are formed. In fact, that’s what happened with XE.
Why are we looking at the recombinant variants now?
In reality, during the two years of the Sars-CoV-2 pandemic, the virus has undergone several changes but each single recombinant or variant does not necessarily have elements such as to transform it into a variant of concern. The reason we are seeing more recombination is likely due to the fact that since the start of the pandemic, more recently more viruses circulated at the same time (Delta, BA.1, BA.2) and the lineages therefore had the opportunity to coinfect. “Also today we are better able to detect recombination: at the beginning of the pandemic there was little genetic diversity in the Sars-CoV-2 virus and the recombinants looked very similar to the non-recombinants because the two parent viruses were almost identical “he explains Tom Peacock virologo all’Imperial Department of Infectious Disease all’Imperial College.
What are the other recombinant variants?
XE is not the only recombinant variant identified so far: there are XA, XB etc, up to XS. Some of these variants were sequenced as early as mid-2020, some have been seen few times while others have hundreds of sequences. So far andthere are two main types of recombinants
: blends of Delta and Omicron (called a little improperly Deltacorn) and mixtures of Omicron subvariants.
In particular, XD and XF are made up of Delta genetic material mixed with BA.1 Omicron. XD it was first detected in France (a few dozen sequences) and then in Germany, Denmark and the Netherlands. Contains a blend of the BA.1 spike protein and the rest of the Delta genome. Initially there was some concern that it may have inherited BA.1’s greater ability to evade our immune defenses and Delta’s high virulence at the same time. Thankfully, XD doesn’t seem to be spreading rapidly today.
Does the XE sub-variant really have to worry?
There is still no evidence to suggest that recombinant viruses are a worse threat to public health than any other variant. However, recombinants should be closely monitored so that they can understand whether they induce changes in virus transmissibility, disease severity, or the ability to escape vaccine-induced immune protection. “If you are vaccinated and otherwise in good health, you shouldn’t worry about it. If you are not vaccinated or have comorbidities, there is cause for concern, ”Badley summarizes
The good news is that there are still relatively few cases of XE. “We have known about the existence of the XE variant since mid-January,” says Badley. “Now, two and a half months later, we’re still seeing cases, but it hasn’t exploded.” To put it into context, he adds: “Omicron was first identified in November and in four weeks it arrived all over the world. Quindi XE doesn’t seem as dominant a new variant as Omicron was».
“It is quite probable that the recombinants that contain the Spike and the structural proteins of a single virus, such as XE act similar to their parental virusHe adds Tom Peacock. It is therefore likely that XE does not act differently than the two parents.
Do the therapies also work against XE?
“BA.1 and BA.2 may escape some of the monoclonal antibody therapies,” so these drugs are unlikely to work as well against XE, says Badley. “We also know that the other therapies used in particular in the outpatient setting, Paxlovid and molnupiravir, should also continue to work against the XE strain”
Do vaccines work against XE?
We know that vaccines work to protect against symptomatic diseases for BA.1 and BA.2, and therefore we have every reason to suspect that vaccination strategies will have activity to protect against symptomatic diseases caused by XE. However, vaccination protection is known to drop, even with respect to hospitalization. The British data indicate that after two and a half months from the recall, about 6% of effectiveness is lost, which then continues to decline over time. The Italian data indicate that among the over 60s three months after the booster the effectiveness drops by 9 percentage points, in line with the English numbers. It is a fact that the more time you spend from the booster the less you are protected by Omicron, without necessarily having to call into question XE which, having Omicron as parents, should not behave differently as regards the effectiveness of the vaccine.
April 11, 2022 (change April 11, 2022 | 15:49)
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