Omicron BA.2 becomes India's dominant Covid-19 variant

More than 80% of the Covid-19 positive samples sequenced in the past four weeks turned out to be BA.2

A new sibling of the Omicron variant of SARS-CoV-2 has taken over the Indian Covid-19 landscape over the past month without altering the epidemic's waning course, even as the World Health Organization described it as a distinct variant of concern.

A technical advisory group of the WHO on Tuesday declared BA.2 sub-lineage of Omicron as a “variant of concern” on the basis of available data on transmission, severity, reinfection, diagnostics, therapeutics and impacts of vaccines.

“Studies have shown that BA.2 has a growth advantage over BA.1. Studies are ongoing to understand the reasons for this growth advantage, but initial data suggest that BA.2 appears inherently more transmissible than BA.1, which currently remains the most common Omicron sublineage reported,” the apex health body said.

But BA.2 has already become the dominant variant circulating in India.

Read | Can Omicron BA.2 cause another Covid surge in India? Here's what experts say

Indian scientists monitoring the Covid-19 epidemic said more than 80 per cent of the Covid-19 positive samples sequenced in the past four weeks turned out to be BA.2.

In Pune, BA.2 was over 85 per cent by the last week of January, but cases continue to drop, suggesting protection from BA.1 infections and vaccination gave reasonable results in securing people from developing the disease, said a scientist associated with Covid genome sequencing work.

The WHO concurs. “Initial data from population-level reinfection studies suggest that infection with BA.1 provides strong protection against reinfection with BA.2, at least for the limited period for which data are available,” the UN body said.

The Pune scientist cautioned that it was preliminary evidence and the new variant needed to be observed closely.

BA.2 differs from BA.1 in its genetic sequence, including some amino acid differences in the spike protein and other proteins.

Omicron is currently the dominant variant circulating globally, accounting for nearly all sequences reported to GISAID, an international database of genetic sequences. At a global level, the proportion of BA.2 sequences has been increasing relative to BA.1 in recent weeks. However, the global circulation of all variants is declining, as per the WHO.

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