Omicron Sub-lineage BA.2 is fast spreading: How worried should we be?

New Delhi, Jan 22: BA.2, a new sub-variant of Omicron has raised concerned that more transmissible strains of the coronavirus could spark larger Covid-19 waves globally.

The UK health authorities have designated the sub-variant, called BA.2, as 'variant under investigation' and are conducting further analysis into a sub-lineage of the Omicron variant of Covid-19 after designating it a variant under investigation (VUI).

The UK Health Security Agency (UKHSA), which monitors data related to the pandemic, said the sub-lineage known as BA.2 shows a low number of cases in the country, with the original Omicron lineage BA.1 still dominant.

The sub-lineage was designated in early December last year and as of January 10 this year, 53 sequences of BA.2 had been identified in the UK.

How many sub-strains dose the Omicron variant have?

According to the World Health Organization (WHO) Omicron, which is also referred to as B.1.1.529, has three main substrains: BA.1, BA.2, and BA.3. As many as 99 per cent of the cases sequenced were found to be containing the BA.1 sub-strain.

The WHO said that the knowledge about B.1.1.529 is still developing, but this lineage is more diverse.

Where have the cases of the BA.2 sub-variant been detected?

Apart from the UK, the BA.2 nicknamed stealth Omicron has been found in Denmark, Norway and Sweden. France and India have also issued warning about the quick spread of the sub-variant.

Denmark is witnessing worst situation for now, where BA.2 has gone from accounting 20 per cent of the cases to 45 per cent between late December and mid-January.

Denmark has been reporting over 30,000 cases this week, 10 times more than the peak in previous Covid-19 wave.

In one of the worrying trend, Vipin M Vashishtha, Member of WHO's Vaccine Safety Net, said on Twitter that BA.2 shares 32 mutations with BA.1 but also has 28 unique mutations of its own.

M Vashishtha has made some observations regarding the BA.2 sub-variant, lets have a look.

What we know about BA.2 sub-variant?

Transmissibility: Consistent growth across multiple countries is evidence BA.2 may be some degree more transmissible than BA.1.

Virulence: Very early observations from India and Denmark suggest there is no dramatic difference in severity compared to BA.1.

Immune evasion: Minimal differences in VE ag. BA.1 & BA.2 and, its also highly likely BA.1 infection will give decent cross-reactivity ag BA.2 infection.

Antigenicity: The Spike RBD mutations are likely to have a fairly minimal impact on antigenicity compared to BA.1.

So how worried should we be?

According to Vipin M Vashishtha, chances of BA.2 to have a substantial impact on the current Omicron wave are low. It is unlikely to cause 2nd Omicron wave!

BA.2 may slowly replace BA.1 over the coming months with a slightly 'optimised' mutational profile.