ScienceNot yet confirmed elsewhere1 publisher2 min readPublished
Existing immunity appears to hold against severe illness as antibody-dodging XFG dominates covid
XFG, the covid lineage behind about 60 per cent of sequenced cases worldwide, escapes antibodies better than earlier variants in lab tests. No rise in severity has been reported so far, and immunity from past infections and vaccines appears to protect most people from serious illness.
The Scientist · Science desk
What happened
- XFG arose when two JN.1 subvariants of Omicron exchanged genetic material, was first detected in early 2025 and has been monitored by the WHO since June 2025.
- In Columbia lab tests, XFG and Nimbus bound to host cells slightly less well than past variants but more than made up for it by evading antibodies.
- Alexander Allen of the UK Health Security Agency said there is no evidence this year's variants make people more ill or spread faster than before.
- A review led by Leena Azhar of Fakeeh College in Jeddah concluded that XFG's changes fit "quiet" evolution and fine-tuning more than a move toward greater virulence.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- constraint Lab antibody escape is tied to how XFG spread, so for the next variant an escape result is a cue to watch hospital data and cannot stand in for a reading of severity.
- exposure With less sequencing, there is less early warning if a heavily mutated strain arises in an immunosuppressed person, the route by which Omicron emerged, Mellis said.
- decision For UK residents last vaccinated years ago, the autumn shot is the way to update older immunity; UKHSA's Allen said it was designed specifically against this year's variants.
Ian Mellis's group at Columbia University tested XFG, Nimbus and a range of other covid viruses against antibodies found in human populations [5]. That design asks one question: how well do the antibodies people already carry stop each virus? It does not follow anyone into hospital. New Scientist reports that XFG's antibody escape is "thought to be" why it became dominant globally [4]. That is a plausible link between a lab property and a spread pattern, and the assay alone cannot confirm it. The report does not put a number on the binding loss or the escape gain [6].
Severity has to be read from hospital data. In the UK, 1,638 covid cases were identified in hospital settings in the first week of October, up from 1,328 the week before [7]. That is 310 more cases, a rise of about 23 per cent in a week [21]. New Scientist calls it part of an expected seasonal rise [8]. Because an autumn rise is expected, last year's figure is the nearer thing to a control, and this year's count sits below it [8].
Those figures are early. "It takes time for something that sweeps through to turn into hospitalisations and for those to be recorded," said Aris Katzourakis at the University of Oxford [10]. Danny Altmann at Imperial College London expects a small effect to appear. XFG's antibody escape, combined with how widespread it is, may leave more people open to serious infection, he said. "That may play out in a few more hospitalisations." [22]
He is not worried beyond that. "I'm not unduly excited or alarmed," Altmann said of the latest variants. "We're still where we thought we were." [13] Six years on from the pandemic's height, he described the situation as "weird, uncharted territory" [19].
I think the evidence supports caution over alarm for XFG. It does not yet show that better antibody escape now comes without worse disease as a general rule. That rule would rest on one lineage, on an assay that measures antibodies alone, and on hospital counts that, by Katzourakis's account, trail the infections behind them [10]. The present calm also depends on immunity built up over earlier years. In Altmann's words, "we're making do with the immunity that we've got on board" [12].
What to watch
- UK hospital-setting covid counts for late October and November, as lagged admissions are recorded, and whether they stay below last year's level.
- A heavily mutated strain emerging outside the current Omicron descendants, the scenario Mellis says could start a new wave of infections.
- Whether sequencing volumes recover enough to give early warning of such a strain.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence55
- Adoption
- Insufficient
- Hype gap+5
- Incentives
- Insufficient
- Confidence45
Claim ledger
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- [1]
A seasonal rise in covid-19 cases in Europe and North America has focused attention on a group of variants called XFG, which have dominated worldwide over the past year.
- [2]
XFG now makes up around 60 per cent of sequenced covid-19 cases worldwide.
- [3]
XFG emerged from an exchange of genetic material between two subvariants of the Omicron lineage JN.1, according to Ian Mellis; it was first detected in early 2025 and the World Health Organization began officially monitoring it in June 2025.
- [4]
In lab tests, XFG is better at evading antibody protection than previous covid-19 variants, which is thought to be why it has become dominant globally.
- [5]
Mellis and colleagues at Columbia University tested a range of covid-19 viruses, including XFG and a variant nicknamed Nimbus, against antibodies found in human populations.
- [6]
Both XFG and Nimbus bound to host cells slightly less well than past variants, but this was more than offset by a greater ability to evade covid-19 antibodies.
- [7]
In the UK, 1638 covid-19 cases were identified in hospital settings during the first week of October, up from 1328 cases the week before.
- [8]
The UK rise is part of an expected seasonal rise and is lower than at the same time last year.
- [9]
"We're not seeing any evidence that [this year's variants] are making people more ill or spreading faster than before,"
- [10]
"It takes time for something that sweeps through to turn into hospitalisations and for those to be recorded."
- [11]
Leena Azhar at Fakeeh College of Medical Sciences in Jeddah and colleagues reviewed what is known about XFG and concluded it exemplifies "quiet" evolution that is more consistent with fine-tuning "than a shift toward greater virulence".
- [12]
"we're making do with the immunity that we've got on board," Altmann says. "That's keeping a lid on it."
- [13]
"I'm not unduly excited or alarmed," Altmann said of the latest variants. "We're still where we thought we were."
- [14]
A more dangerous strain could still emerge, for example if many mutations accumulate in a single immunosuppressed individual, which is how Omicron originated. "There is a risk that a new strain could emerge that causes a wave of infections again," says Mellis.
- [15]
There is now far less monitoring that could provide early warning of a more dangerous strain, and the amount of sequencing data has fallen, according to Mellis.
- [16]
Allen said this year's autumn covid-19 vaccine has been specifically designed to protect against this year's variants.
- [17]
For most people, existing immunity from previous vaccinations and infections appears to be enough to protect against serious illness.
- [18]
So far, no evidence of increased disease severity, hospitalisations or deaths from XFG has been reported.
- [19]
"we're in this weird, uncharted territory," says Danny Altmann at Imperial College London, six years on from the height of the pandemic.
- [20]
Many people in the UK haven't been vaccinated for several years.
- [21]
UK covid cases identified in hospital settings rose by 310, about 23 per cent, from the last week of September to the first week of October.
- [22]
Altmann said XFG's ability to evade the immune response, on top of how widespread it is, may mean more people will be susceptible to serious infection: "That may play out in a few more hospitalisations."
ReportedInsufficientSource: Danny Altmann, Imperial College London2 sources— create a free account to open themView cited source
Sources
1 independent publisher whose own reporting we read for this story.
- newscientist.comDoes each new covid-19 variant pose a significant threat?
1 article · October 9, 2026
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