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New Covid-19 variants are spreading around the world and stoking fears of a summer surge in cases n the US, in the latest sign of the infectious disease’s ability to mutate and potentially threaten collective immunity.
KP. 2, one of several so-called FLiRT variants — the word derives from the names of the mutations in the variants’ genetic code — has become the dominant coronavirus strain in the US since first emerging in March.
In the two weeks to May 11, KP. 2 accounted for 28.2 per cent of cases, up from just 3.8 per cent in the two weeks to the end of March, according to the latest data from the US Centers for Disease Control and Prevention. The KP1.1 variant has also grown rapidly to account for 7.6 per cent of infections.
The agency is closely monitoring the FLiRT variants — including the KP strains and previously dominant JN.1 strain that are all offshoots of the dominant Omicron Covid strain — but does not believe there is evidence that it will drive a surge in cases of severe disease.
Four-and-a-half years after the outbreak of the pandemic, caseloads in the US have in recent months fallen close to record lows. But while many infectious disease experts do not expect a surge in hospital admissions, they caution this new cluster of variants could drive a summer wave of infections.
A key question is how effective current vaccines will be against the new strains. Lawrence Young, a virologist at Warwick university, said booster shots would continue to give worthwhile protection, at least against severe disease.
However William Schaffner, an infectious disease specialist at Vanderbilt university in Nashville, Tennessee, argued that protection “is not as guaranteed against these subvariants because the mutations are a little bit more distant from the kind of antibody protection we got from prior infection and from vaccination”.
“But that evidence is from lab studies, we need to see what happens in the field,” added Schaffner.
The US Food and Drug Administration’s vaccines advisory committee will meet at the end of the month to discuss recommendations for the variant mix of next winter’s Covid vaccines. It postponed the meeting from earlier in May so it could compile more data on the latest strains.
In Europe, the World Health Organization said FLiRT variants had been detected in 14 countries across Europe as well as Israel.
However, the European Centre for Disease Prevention and Control said Covid activity “remained low” across the continent “albeit with a small number of individual countries showing slight increases in detections from very low levels”.
It had also observed “a limited number of detections” for JN. 1.7 and KP. 2, the two variants which had increased in proportion in the US.
Officials from the UK Health Security Agency said on Friday that several of the FLiRT strains were circulating in the UK at low levels, although some appeared to be growing as a proportion of sequenced cases.
Young said the latest data indicated that UK infections with FLiRT variants, which had “outcompeted some of the other variants”, were likely to be similar to levels seen in the US. The strains were also becoming more prevalent in other countries including Canada, Australia, Thailand and India, he added.
Paul Hunter, professor of medicine at the University of East Anglia, pointed to latest UKHSA data suggesting hospitalisations were currently at stable levels and while there had been a slight overall increase in positive cases he stressed that a surge in infection was unlikely.
However, he added that while there was scant evidence to suggest the FLiRT variants were intrinsically more infectious than previous dominant strains, they probably had a slight immune advantage — “and in a population with waning immunity, that’s likely to be contributing to the spread of the virus”.
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