BA.2 – which the UK Health Security Agency (UKHSA) has marked as a “variant under investigation” – is a sub-lineage of the Omicron strain, BA.1, with early data suggesting it may be both more transmissible and better able to evade vaccines than previous Covid variants.
The WHO said this week that BA.2, “which differs from BA.1 in some of the mutations, including in the spike protein, is increasing in many countries”.
The agency added: “Investigations into the characteristics of BA.2, including immune escape properties and virulence, should be prioritised independently and comparatively to BA.1.”
BA.2 has not yet caused enough concern to be classified as a “variant of concern” – as both Omicron and Delta were – but because it is spreading in so many countries, the WHO has asked officials to monitor it closely.
As of last Friday, the new variant was already thought to be in at least 40 countries, including the UK, Denmark, Singapore, India and the US.
In the UK, some 426 cases have been detected since the new lineage was first designated in December. Although that number may seem small in comparison with the tens of thousands of daily cases of Covid-19 over the last two months, it is thought the real figure of BA.2 will be many times higher because only a fraction of infections are checked for variations.
Meanwhile, scientists in Denmark believe more than 45 per cent of all new infections in the country are now related to the new variant. WHO representatives are in Copenhagen as a result, investigating BA.2, which has been nicknamed “stealth Omicron” due to one of its key differences from the original Omicron variant.
That variant was relatively easy to track because of a specific quirk – the deletion of a spike gene – made it stand out on the widely-used PCR tests without the need for extra genome sequencing.
BA.2 does not appear to have this feature, though, making it more difficult to monitor.
Despite this, experts do not appear to believe the new variant will cause another major wave of infections.
Early reports in Denmark indicate it is no more deadly than its parent – Omicron – just more transmissible. It comes as the country’s new Covid infections reached record highs, with more than 30,000 new cases seen every day this week – 10 times more than in previous wave peaks.
Still, Dr Tom Peacock, a virologist at Imperial College London, told the Daily Mail that BA.2 is unlikely to be more severe than previous versions of the killer virus.
He said he believes the variant will not have a “substantial impact” on the current Omicron wave, which the UK and most other countries are now slowly recovering from.