The Omicron variant sub-lineage known as BA.2 has been designated a variant under investigation ( VUI-22JAN-01) by the UK Health Security Agency (UKHSA).
Overall, the original Omicron lineage, BA.1, is dominant in the UK and the proportion of BA.2 cases is currently low. The designation was made on the basis of increasing numbers of BA.2 sequences identified both domestically and internationally. There is still uncertainty around the significance of the changes to the viral genome, and further analyses will now be undertaken.
To date, there have been 426 cases of Omicron BA.2 confirmed by Whole Genome Sequencing (WGS), with the earliest dated 6 December 2021.
The areas with the largest number of confirmed cases are London (146) and the South East (97). Data for the devolved administrations will follow in due course.
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Early analyses suggest an increased growth rate compared to BA.1, however, growth rates have a low level of certainty early in the emergence of a variant and further analysis is needed.
In total, 40 countries have uploaded 8,040 BA.2 sequences to GISAID since 17 November 2021. At this point it is not possible to determine where the sublineage may have originated. The first sequences were submitted from the Philippines, and most samples have been uploaded from Denmark (6,411). Other countries that have uploaded more than 100 samples are India (530), Sweden (181), and Singapore (127).
Omicron BA.2 lacks the genetic deletion on the spike protein which produces S-gene target failure (SGTF) in some polymerase chain reaction (PCR) tests, which has been used as a proxy for Omicron cases previously.
Dr Meera Chand, COVID-19 Incident Director at UKHSA, said:
It is the nature of viruses to evolve and mutate, so it’s to be expected that we will continue to see new variants emerge as the pandemic goes on. Our continued genomic surveillance allows us to detect them and assess whether they are significant.
So far, there is insufficient evidence to determine whether BA.2 causes more severe illness than Omicron BA.1, but data is limited and UKHSA continues to investigate.
Case rates remain high throughout the UK and we must remain vigilant and take up vaccinations. We should all continue to test regularly with LFDs and take a PCR test if symptoms develop.
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