A new Danish study has confirmed that the BA.2 subvariant of Omicron is much more infectious than the ‘original’ BA.1 lineage, which was itself transmissible enough to fuel a new wave of infections around the world.
How much more transmissible is BA.2?
The new research, conducted by scientists from Statens Serum Institut (SSI), Copenhagen University, Statistics Denmark and Technical University of Denmark, has shown that the rapid spread of BA.2 could be linked to its
“inherent increased transmissibility”. BA.2 is already the dominant Covid strain in Denmark. Seattle-based virologist Trevor Bedford, who is tracking the emergence of new Covid variants, recently said that, while the ‘original’ Omicron strain remains dominant in the world, its subvariant BA.2 “has become predominant in Denmark and India, and is spreading elsewhere.” Indeed, the subvariant has already been reported in several countries, including the US and the UK. “In each country and across time” the epidemic growth rate of BA.2 is greater than that of BA.1, Bedford noted.
Is it more dangerous?
According to the Danish paper, which has yet to be peer-reviewed, the risk of catching BA.2 after being exposed to it within the household is 39%, some 10% higher than BA.1.
The study’s lead author Frederik Plesner clarified to Reuters that these numbers suggest that BA.2 is about 33% more infectious than BA.1. The researchers also noted indications that BA.2 has greater “immune evasive properties” than BA.1, given it was relatively better at infecting vaccinated persons. These properties, the scientists conclude, “further reduce the protective effect of vaccination against infection.” However, vaccinated and vaccine-boosted people were less likely to be infected with either substrain than a person who was not inoculated against Covid. There is good news from the Danish research: apparently BA.1 is not associated with an increased risk of hospitalization. As Danish Health Minister Magnus Heunicke said last week, “there is no evidence that the BA.2 variant causes more disease,” despite it being more contagious.
Are there other variants of Omicron?
The first known version of Omicron is called B.1.1.529 and was named a variant of concern by the World Health Organization (WHO) on November 26. It has since been found to have mutated into a number of strains: BA.1, responsible to date for more than 98% of all known Omicron cases and which is easily identifiable due to it lacking one of the target genes in PCR testing; and BA.2, which, in Bedford’s words, is now
Another Omicron subvariant, called BA.3, has also been identified but, at the moment, is not spreading as fast as any of its closest ‘relatives.’
The four Omicron lineages (B.1.1.529, BA.1, BA.2 and BA.3) are being closely monitored by the WHO, which has warned that “the overall risk related to Omicron remains very high.”