An offshoot of the Omicron coronavirus variant, known as BA.2, is being investigated by England’s public health body over concerns that it may be even faster spreading than the original version.
The UK Health Security Agency said it was designating the Omicron offshoot a ‘variant under investigation’ because of “increasing numbers of BA.2 sequences identified both domestically and internationally”.
Early analysis suggests the BA.2 sub-variant may have an “increased growth rate” over the earlier form of Omicron, officially designated as BA.1, according to UKHSA, which stressed that there is a “low level of certainty early in the emergence of a variant”. Moreover, BA.2 has not been named a ‘variant of concern’ — the highest risk ranking for new strains.
About 426 cases of the Omicron offshoot have been sequenced in the UK, with the first found in early December. Only 0.26 per cent of Covid-19 cases sequenced in the UK in the week ending January 26 were BA.2.
Globally, roughly 8,000 sequenced BA.2 genomes have been uploaded to the international genome repository Gisaid.
The offshoot was first identified in the Philippines in early December a few weeks after the Omicron surge began, but it appears to be outcompeting its sister strain in several territories. Denmark and India now have a high prevalence of BA.2.
“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,” said Dr Meera Chand, UKHSA Covid-19 incident director.
She added: “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.”
When the sub-variant first emerged, experts expressed concern that it may be more difficult to track than the original version of Omicron. Because of a genetic quirk, the original Omicron variant could easily be distinguished from the previously dominant Delta strain with a PCR test because it did not possess one of the three coronavirus gene targets — the S gene.
BA.2 does possess the S gene, meaning full genome sequencing is required to distinguish it from Delta. However, as Omicron is now the dominant variant, this is less of a problem.
Dr Tom Peacock, a virologist at Imperial College London who was one of the first scientists to raise the alarm about the original version of Omicron, told the FT he did not believe BA.2 was a “major cause of concern” but added it was “definitely worth keeping an eye on”.
Even if the sub-variant could outcompete the original Omicron or was more severe it would be “less likely to cause a big spike in hospitalisations and deaths in the UK as the total case numbers would be depressed by prior immunity to BA.1”, he said.
Sajid Javid, UK health secretary, stressed that because of the UK’s vaccine rollout “the number of people severely affected by Covid-19 is low”.
“We are learning to live with this virus — and thanks to our world-leading surveillance system we can rapidly detect and carefully monitor any genetic changes to Covid-19,” he added.