Pune: All countries should keep a close eye on Omicron’s BA.2.75 subvariant as there still aren’t enough samples globally to analyse its severity, the WHO’s chief scientist Dr Soumya Swaminathan told the media agency on Saturday.

Dr Swaminathan said India is among the first few countries to report the variant, which has mutations in the receptor-binding domain of the spike protein.

“This being the key part of the virus that attaches itself to the human receptor, we need to keep a watch on its behavior. But it’s still too early to tell if the subvariant has properties of additional immune invasion or is clinically more severe,” she said.

So far, 10 states, including Maharashtra and Delhi, have reported BA.2.75. Given the detection levels, Dr Swaminathan said all data on hospitalisations and deaths of Covid patients (including age, sex and vaccination status) should be collected to determine duration of vaccine protection. 

“This is the only way to decide frequency of booster doses and which groups may go on to require a fourth dose,” she said.

INSACOG scientists, who met on Friday to discuss the subvariant, said early data showed most people with BA.2.75 were either asymptomatic or had mild Covid. They also said so far they have not seen any infection clusters of the subvariant.

“It’s still too early to call this subvariant ‘severe’. It has also not caused clusters, despite spread in several states,” an INSACOG expert said. Besides Delhi and Maharashtra, BA.2.75 has been detected in Kerala, Tamil Nadu, Karnataka, Andhra Pradesh, Telangana and Uttar Pradesh.

State genome sequencing head Dr Rajesh Karyakarte said a preliminary study of 75 patients of BA.2.74, BA.2.75, and BA.2.76 in the state showed all had only mild symptoms. But more studies are needed, he added.

Dr Krishanpal Karmodiya, assistant professor, Indian Institute of Science Education and Research (IISER), said it will be known in a week or two if the subvariant is leading this surge. 

“And initial indications are that most of the cases are either asymptomatic or mild,” he said.

Dr Rajeev Jaydevan, co-chairperson of the IMA’s task force said it’s natural to expect more sub-lineages of Omicron. 

“This sub-lineage has drawn attention because of a unique combination of mutations, but that alone cannot predict clinical outcome. There are no reports of severe disease from the limited samples that are available, less than 100. Large-scale genomic sampling from different parts of the country is essential,” he said.