The World Health Organisation (WHO) has classified the JN.1 COVID strain as a “variant of interest”.
Announcing the new classification, the UN agency stressed the risk posed by the strain is considered “low”.
“Based on the available evidence, the additional global public health risk posed by JN.1 is currently evaluated as low,” WHO said.
It said existing vaccines continued to be effective against severe disease and death from JN.1 and other circulating variants.
The classification comes as COVID cases rise in the UK in the run-up to Christmas.
The latest data, which covers the week ending 9 December, shows COVID cases increasing by 39% in England on the previous week.
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JN.1 is a sub-lineage of the BA.2.86 Omicron variant.
It has one mutation in its spike protein – which dictates how easily it can infect our cells – compared to BA.2.86. But there are several other mutations elsewhere.
Speaking to Sky News earlier this month, Professor of innate immunity at the University of Cambridge, Clare Bryant, said the changes were likely to mean JN.1 evades our immune systems more easily – and replicates faster.
“The change in the spike protein will probably correlate to it being more infectious,” she said.
However, there has so far been no indication of increased disease severity, according to Professor Nicolas Locker, a virologist at the Pirbright Institute.
“I think we’re just seeing the natural evolution of COVID and I don’t think there’s anything right now we should be overly worried about,” he said.
“These are very small changes in comparison to the ones between Omicron and the previous set of variants. And we haven’t seen a change in symptoms or severity.”
According to the US Centers for Disease Control and Prevention’s (CDC) latest projections, JN.1 currently makes up an estimated 15% – 29% of cases in the UK.
