Update on BA.2 Omicron Subvariant
February 19, 2022 — According to a pre-print Japanese lab study posted this week on bioRxiv, the BA.2 Omicron subvariant is not only faster at spreading than the BA.1 Omicron variant, but may also cause more severe COVID-19 disease.
To place the study in context, during the two-week period from January 30, 2022 thru February 12, 2022, the incidence of BA.2 subvariant infections in the United States rose from less than 1% of all coronavirus cases to an estimated 4%.
BA.2 Omicron Subvariant Shows Increased Spread
The study findings suggest BA.2 subvariant has considerable transmission improvement over the BA.1 Omicron Variant. A statistical analysis performed by The University of Tokyo researchers reveals the effective reproduction number of the BA.2 Omicron subvariant as 1.4-times higher on average than the BA.1 Omicron variant. In the rear world, the BA.2 subvariant follows the initial spread of BA.1 Omicron variant. Even so, the subvariant has been observed to start outcompeting BA.1 Omicron. The Japanese study authors note “the lineage frequency of BA.2 increased and exceeded that of BA.1 since January 2022 in multiple countries, such as Philippines, India, Denmark, Singapore, Austria, and South Africa.”
In the lab, researchers found the BA.2 subvariant could replicate itself in cells more rapidly than the BA.1 Omicron variant. BA.2 was also more proficient at making cells cling together. This characteristic enabled the virus to produce larger clusters of cells, called syncytia, than the BA.1 Omicron variant. That’s concerning not only as these bunches then become more proficient at producing additional copies of the virus (higher load levels), but because the creation of syncytia is also thought to be a reason why other strains of SARS-CoV-2, like Delta, were so destructive to the lungs.
BA.2 Omicron Subvariant May Cause More Severe Illness
Further infection experiments using hamsters showed the BA.2 subvariant was more pathogenic – capable of causing disease – than the BA.1 Omicron variant. When researchers infected hamsters with BA.2 subvariant and BA.1 Omicron variant, the animals with administered BA.2 virus exhibited more health disorders such as body weight loss than those infected with BA.1 virus. In tissues samples, the lungs of BA.2-infected hamsters had more damage than those infected by BA.1. The study also found that the amount of BA.2 virus was higher in the hamsters’ lungs than that of BA.1 virus.
BA.2 Omicron Subvariant Shows Significant Vaccine Escape
Like the BA.1 Omicron variant, researchers found the BA.2 subvariant of Omicron to largely escape the immunity induced by COVID-19 vaccines. BA.2 was also nearly entirely resistant to some monoclonal antibody treatments, study authors say, including sotrovimab — a monoclonal antibody used against the BA.1 Omicron variant.
BA.2 More Resistant to Previous Omicron BA.1 Variant Infection
Researchers also observed the antigenicity of the BA.2 subvariant to differ from the BA.1 Omicron variant. The researchers infected hamsters with the BA.1 Omicron virus and then obtained convalescent sera (blood samples) after their bodies had produced antibodies. They then subjected the Omicron BA.1 antibodies to BA.1 and BA.2 viruses. The researchers observed the BA.2 strain was 2.9-times more resistant to the Omicron BA.1 antibodies than BA.1 strain. Next, they tested this finding in mice by injecting them with cells conveying the spike protein of the BA.1 Omicron variant and once again tested their antibodies against BA.1 and BA.2 viruses. This time they noticed the BA.2 virus subvariant was 6.4 times more resistant than the BA.1 Omicron virus variant.
Conclusions
The study notes BA.2 is not only highly mutated as compared to the ancestral SARS-CoV-2 virus that emerged in 2019 in Wuhan, China, but also has dozens of gene alterations from the original Omicron strain — making it as distinct from the BA.1 variant as the Alpha, Beta, Gamma and Delta variants were from each other. Although BA.2 is currently considered an Omicron subvariant, the authors suggest with its genomic sequence being heavily different from BA.1 along with its increased transmissibility rate and pathogenicity over BA.1, the BA.2 subvariant should be recognized as a unique variant of concern and monitored separately from the Omicron BA.1 variant.
Opposite to these findings, the World Health Organization (WHO) on Thursday noted that while the BA.2 subvariant is more infectious than the more common BA.1 Omicron variant, between the two strains there is no change in virulence (severity of disease). “Among all subvariants, BA.2 is more transmissible than BA.1. However, there is no difference in terms of severity,” Maria Van Kerkhova, COVID-19 Technical Lead at WHO said in a video.
According to a WHO update published this week, the BA. 2 subvariant now accounts for 21.1% of Omicron cases worldwide.
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New COVID-19 Variant Facts: What We Know So Far. 4U Health. Updated December 7, 2021.
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Ditch Nose Swabs for a Home Saliva PCR Covid Test Kit. 4U Health. Updated December 6, 2021.
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Important notice
Updated: February 19, 2022
