The UK Health Security Agency has designated the Omicron variant sub-lineage, known as BA.2, as a variant under investigation – with current case rates very low.
Just 53 sequences had been identified in the UK by 10 January, according to the HSA, which said it was doing further analysis.
Initial studies from Denmark – where it’s quickly taken hold and now makes up around half of Omicron cases – show no difference in hospitalisations between ‘original’ Omicron and BA.2.
Vaccines are also expected to be effective against BA.2 in fighting severe illness, according to Danish health officials.
However, it is unclear whether it could be even more transmissible and more data is needed to test that possibility.
BA.2 is S-gene positive – which may make it harder to identify as Omicron than BA.1, which accounts for 99% of cases.
S-gene target failure helps identify Omicron and can be picked up PCR tests, because as a rule Delta cases have the S-gene and Omicron cases don’t.
Some 2,093 sequences of BA.2 had been recorded on an online database from 22 countries – including the UK, the HSA said last week.
Denmark’s Statens Serum Institut, part of its ministry of health, has said hospitalisations appear to show no difference for the two Omicron lineages but that “analyses regarding infectiousness and vaccine efficiency etc. are ongoing”.
“It is expected that vaccines also have an effect against severe illness upon BA.2 infection,” it added.
However, some experts have said it’s possible it could spread quicker than the ‘original’ Omicron.
“Consistent growth across multiple countries is evidence BA.2 may be some degree more transmissible than BA.1,” tweeted Tom Peacock, a virologist from Imperial College London.
“Unfortunately this is really where the evidence mostly ends – we do not currently have a strong handle on antigenicity, severity or a much evidence for how much more transmissibility BA.2 might have over BA.1 – however we can make some guesses/early observations,” he added.