Early data suggests that the BA.2 variant could be 1.5 times more infectious than the original Omicron strain
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UK health officials are officially monitoring a new strain of Covid-19, dubbed “Stealth Omicron”, which appears to be more contagious than the original Omicron strain.
Early data suggests that BA.2, a subvariant thought to have arisen from a mutation of the Omicron coronavirus variant, may be more transmissible and better able to evade vaccines than the more common BA.1 sublineage.
Currently, the BA.1 lineage accounts for 98% of all cases globally, but in Denmark, BA.2 has grown rapidly.
In the last week of 2021, it accounted for 20% of all Covid-19 cases. For the second week of 2022, it represented 45% of the cases. On Wednesday, it was reported that BA.2 had become the dominant strain in Denmark.
In a national address on Wednesday, Danish Health Minister Magnus Heunicke said: “There is no evidence that the BA.2 variant causes more disease, but it must be more contagious.”
Initial calculations by Denmark’s leading infectious disease authority, Statens Serum Institut, show that BA.2 could be 1.5 times more infectious than BA.1.
So far, early data has not shown a difference in hospitalization risk for BA.2 compared to BA.1.
“There are some indications that it is more contagious, especially to the unvaccinated, but it can also infect more people who have been vaccinated,” SSI technical director Tyra Grove Krause said at Wednesday’s briefing. .
The BA.2 has been dubbed the “stealth Omicron” as it poses a challenge for scientists to track down, unlike the original Omicron which excelled in widely used PCR tests without the need for additional genome sequencing. The new strain shows up as positive for the S gene in the PCR tests, while BA.1 does not.
According to the World Health Organization, BA.2 sequences have been reported in more than 40 countries, including the United Kingdom, Sweden, Norway, Singapore, and India.
On Friday, the UK Health Security Agency designated BA.2 as a “variant under investigation”, one level below a “variant of concern”, saying it could have a growth advantage.
“The nature of viruses is to evolve and mutate, so hopefully we will continue to see new variants emerge,” said Dr. Meera Chand, UKHSA incident manager.
“Our ongoing 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 disease than omicron BA.1, but data is limited and UKHSA is continuing to investigate.”
In the UK, some 426 cases of the BA.2 sublineage have been sequenced, according to Reuters, with UKHSA saying early analyzes suggested a higher growth rate compared to BA.1.
Tom Peacock of Imperial College London, one of the first virologists to raise the alarm about Omicron, tweeted that “Very early observations from India and Denmark suggest no dramatic difference in severity compared to BA.1. These data should become more solid (one way or another) in the coming weeks.”
He added that “there are likely to be minimal differences in the effectiveness of the vaccine against BA.1 and BA.2. Personally, I am not sure that BA.2 is going to have a substantial impact in the current wave of the Omicron pandemic.
“Several countries are close to, or even beyond the peak of the BA.1 waves. I would be very surprised if BA.2 caused a second wave at this point. Even with slightly higher transmissibility, this is absolutely not a Delta-change. Omicron and instead is likely to be slower and more subtle,” he continued.
George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.