WHO tracks two new Omicron sub-variants

Tribune News Service

Aditi Tandon

New Delhi, April 17

The World Health Organization (WHO) on Sunday said it was tracking two new Omicron sub-variants BA.4 and BA.5 to assess their immunity escape potential.

The sub-variants, WHO chief scientist Soumya Swaminathan said, needed careful clinical, epidemiological and immunological studies for their properties. “The WHO is following this closely,” she said.

Leading the investigations is Tulio de Oliveira, Director of Centre for Epidemic Response and Innovation, South Africa, where a network of researchers are studying whether new lineages BA.4 and BA.5 escape immunity from Covid vaccines and prior infections.

Leading journal Nature this week documented the path-breaking efforts in South Africa which was the first to report Omicron.

Called BA.4 and BA.5, the sub-variants are now growing in prevalence in South Africa, where Oliveira is leading one of the world’s strongest genomic surveillance programmes for SARS-CoV-2.

The sub-variants were first spotted on April 1 by a bioinformatician on de Oliveira’s team who saw researchers at the centre’s lab and at the National Institute for Communicable Diseases in Johannesburg had flagged several abnormal SARS-CoV-2 genome sequences in their latest batch of data.

“The sequences had a few notable mutations in the region of SARS-CoV-2 that encode its spike protein. Because the spike protein is key to the virus invading cells, Oliveira’s team member recognised an urgent need to hunt for these mutations in all of the genomes sequenced in the country over the past few months to see if they had skirted by unnoticed,” Nature says.

Working through the weekend, Oliveira and his colleagues found that a month earlier — during the first week of March — the BA.4 and BA.5 sequences comprised around 5% of the roughly 500 genomes sequenced in South Africa.

By the first week of April, the portion had risen to 50%. That week, an international virus classification group determined that BA.4 and BA.5 were indeed their own separate lineages on the Omicron family tree and gave them their names.

Lorenzo Subissi, a virologist at the WHO, says the agency is tracking the two sub-lineages. “But before it draws any conclusion about whether they pose an additional threat compared with other Omicron variants, it needs to learn more from epidemiological studies of people. Immunologists are also approaching the question of immune escape by exposing samples of BA.4 and BA.5 to blood drawn from people previously infected with SARS-CoV-2 and people who have been vaccinated,” the WHO virologist said, as quoted by Nature.

Covid 19 cases have in recent days spiked in various parts of the world, including China. Nationally, India has been seeing over 1,000 daily cases for four days now. In the last 24 hours 1,150 cases were seen while active cases rose further to 11,558.

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