Still Too Early To Know If Omicron Subvariant BA.2.75 Can Be More Clinically Severe: WHO Chief Scientist Soumya Swaminathan

Omicron Subvariant BA 2.75: Swaminathan said that BA.2.75 was first reported from India, & that the subvariant seems to have a few mutations on the receptor binding domain (RBD) of the spike protein.

Soumya Swaminathan, chief scientist at the World Health Organization (WHO), has said that there is an emergence of a potential Omicron subvariant. The new strain has not yet been given an official name, but some people are referring to it as BA.2.75. 

In a video shared by the WHO, Swaminathan said that BA.2.75 was first reported from India and then from about 10 other countries. She added that there are limited sequences available to analyse. 

The WHO Chief Scientist said that it is too early to know if the new Omicron subvariant can be more clinically severe. 

"It is still too early to know if this subvariant has properties of additional immune invasion or indeed of being more clinically severe — we don't know that," she said.

Swaminathan explained that the subvariant seems to have a few mutations on the receptor binding domain (RBD) of the spike protein. The RBD is a key part of SARS-CoV-2 that attaches itself to the human receptor, called ACE2. "So, we have to watch that," Swaminathan said.

"So, we have to wait and see and of course we are tracking it," she added.

Swaminathan further said that the Technical Advisory Group on SARS-CoV-2 Evolution (TAG-VE), which acts as an advisory body to the WHO, is constantly looking at the data from around the world. 

She said that at any time, if there is an emergence of a virus that looks very different from a previous one, enough to be called a separate variant of concern, the TAG-VE committee will do that.

The Indian health ministry has not yet confirmed the detection of the subvariant in the country. Dr Shay Fleishon, with the Central Virology Laboratory at Sheba Medical Center in Tel Hashomer, wrote in a series of tweets that 85 sequences of BA.2.75 have been obtained so far, mainly from 10 states in India and seven countries. He said that no transmission could be tracked based on sequences outside India yet. 

Geographic Distribution Of BA.2.75

Fleishon said that BA.2.75 may be “alarming” in nature. He posted a table depicting the geographic distribution of the cases. The capital of India, Delhi, was found to have one case of the new subvariant. The states of Haryana, Himachal Pradesh, Jammu and Kashmir, Karnataka, Madhya Pradesh, Maharashtra, Telangana, Uttar Pradesh and West Bengal have six, three, one, ten, five, twenty-seven, two, one, and thirteen cases respectively. 

Meanwhile, Japan, Germany, the United Kingdom, Canada, United States, Australia, and New Zealand have one, two, six, two, two, one, and two cases of new subvariant respectively.

Fleishon further wrote that it is “too soon” to say whether BA.2.75 will be the next dominant variant. However, he believes that BA.2.75 is "alarming" because it may imply a trend to come.

What We Know About BA.2.75 So Far

Tom Peacock, a virologist at the Imperial Department of Infectious Disease, London, wrote on Twitter that it is worth keeping a "close eye" on BA.2.75. This is because the new variant has lots of spike mutations, and is apparently growing rapidly and widely spreading across geographical regions, he explained.

Bloom Lab, a Seattle-based lab studying molecular evolution of proteins and viruses and associated with Fred Hutch research institute in the United States, wrote in a tweet last week that the institute said the subvariant is flagged by Tom Peacock is "worth tracking", as it has appreciable antigenic change relative to its parent BA.2. According to the lab, the two key mutations are G446S and R493Q. 

The lab wrote on Twitter that G446S is at one of the most potent sites of escape from antibodies elicited by current vaccines that still neutralise BA.2. It added that for immunity from vaccines or early infections, adding G446S to BA.2 will decrease neutralisation.

According to Bloom Lab, there is an evolutionary role for R493Q, which is seen in BA.2.75 as well as BA.4 and BA.5. Though R493Q is not a major antigenic mutation, it enables F486V mutation in BA.4 and BA.5, and G446S mutation in BA.2.75. 

R493Q increases the virus's affinity to ACE2, which is the receptor for the SARS-CoV-2 viral entry. 

The lab stated that BA.2.75 will have antibody-espace similar to that for BA.4 and BA.5 with respect to current vaccines.