BA.2 Omicron sub-variant: What is it, how transmissible is it, and how many cases in Scotland are there?

The BA.2 strain of the BA.1 Omicron strain - also known as ‘stealth Omicron’ - was found in Britain after it was first detected in Europe.

Studies are now ongoing to learn more about this new sub-variant.

What is BA.2?

Both BA.1 and BA.2 share similar characteristics - with a few different mutations - meaning they have both been classed as Omicron.

BA.2 was found to have a different S-gene mutation compared to that of BA.1.

When a PCR test is carried out, scientists are able to distinguish between the two because the BA.2 cases will show positive for the S-gene while the BA.1 case will not.

It was first designated as an Omicron variant on December 6, with scientists confirming that cases of the strain had been discovered in the UK since January 10.

It has now become the dominant strain in some countries around the world.

How many cases are there in Scotland?

First Minister Nicola Sturgeon gave an update to MSPs at Holyrood on Tuesday.

She said that 26 cases of BA.2 had been confirmed in Scotland. However, she said this would be an ‘underestimate’ on the number of cases.

Is it more dangerous than BA.1?

A preliminary assessment found no evidence that vaccines would be any less effective against symptomatic disease for BA.2.

Reports also indicate that there is no difference in the severity of the infection.

However, there are indications that it could be more transmissible than BA.1.

What did Nicola Sturgeon say?

She told Holyrood: “As members will recall, with the main Omicron variant, what is called the S Gene is absent in PCR tests.

“However, in BA.2 cases the S Gene shows up.

“In the last week, the proportion of PCR tests with an S Gene dropout - which indicates the main Omicron variant - has declined, with a corresponding increase in the proportion of tests showing S Gene positive results.

“This could be accounted for by Delta cases which also show positive S Gene results.

“However, it may also indicate increasing transmission of the BA.2 sub variant.

“Genomic sequencing is being used to investigate this further.

“So far, I can confirm that in Scotland, 26 cases of BA.2 have been confirmed through genomic sequencing - but we expect this number to increase as more sequencing results are reported. And given that not all tests are genomically sequenced, it will be an underestimate of the presence of this sub variant here.

“It is important to stress that, at this stage, there is no evidence that BA.2 causes more severe disease than the main Omicron variant.

“Nor, at this stage, is there any evidence that BA.2 has any greater ability to escape the immunity conferred by vaccines or previous infection.

“However, BA.2 does appear to have the ability to out-run the main Omicron variant, which may indicate that it is more transmissible.

“Investigations into this are ongoing, both in the UK and in other countries, like Denmark, where the sub-variant has been circulating for longer.

“At the moment, therefore, this BA.2 sub-variant is not a cause for any alarm, nor a cause to change our approach, but it does warrant further study.

“It also a reminder that the course of this pandemic - of any pandemic - does remains uncertain.

“So even as we get back to normal life, we must take care and remain vigilant.”