A new COVID-19 variant that could soon become the UK's new dominant strain is the most resistant to immunity yet, the World Health Organization (WHO) has warned.
XBB.1.5 is a heavily mutated, sub-lineage of Omicron and is able to bind to cells in the body much more effectively than its predecessors. It is behind a rapid surge of infections in the US.
Dubbed "the Kraken", it was believed to be behind around 30% of the country's cases in the first week of January, compared to just 2% at the start of December.
So far it has been reported in 38 countries, including in the UK, where officials warn it is likely to become the most dominant version of COVID.
In a statement, the WHO said that XBB.1.5, along with its fellow XBB variants, and BQ.1 variants – all part of the Omicron "family" – are "the most antibody-resistant variants to date".
However, while the new variant – first detected in New York in October – may contribute to a rise in cases globally, it is not expected to make people more unwell than any other previous versions of COVID.
The WHO states: "XBB.1.5 does not carry any mutation known to be associated with potential change in severity".
A recent rise in COVID-19 cases in the UK has led to increased hospital admissions this winter.
This, along with an increase in flu and Strep A admissions, are adding to intense pressure faced by the NHS, but critics of the government say more than a decade of underfunding has led to the crisis point.
A new technical briefing from the UK Health Security Agency (UKHSA) states that XBB.1.5 “remains at very low prevalence in Britain, so estimates of growth are highly uncertain”.
However, it adds: “CH.1.1 and XBB.1.5 are currently the variants most likely to take over from BQ.1 as the next dominant variant in the UK, unless further novel variants arise.
The health body added that neither of these strains have been designated as variants of concern, and that it is "constantly monitoring" the situation.
UKHSA director of clinical and emerging infections, Dr Meera Chand, said: “Vaccination remains our best defence against future COVID-19 waves, so it is still as important as ever that people come forward and take up all the doses for which they are eligible as soon as possible.”