New XBB COVID-19 strain in 4 Indian states: How wary should we be of this 'immunity-evasive' variant?

XBB, a new Omicron subvariant that accounts for half of the daily COVID-19 cases in Singapore presently, has been reported in four Indian states.

Maharashtra reported its first five cases of the XBB strain on Thursday (13 October), as per Times of India (TOI). In around two weeks, Odisha accounts for 33 XBB infections, West Bengal logged 17 and Tamil Nadu has 16 such cases, reports TOI. 

XBB, a “recombinant lineage” between two Omicron sublineages, BA.2.75 and BJ.1, has been reported in other countries including the United States, Australia, Bangladesh, Denmark and Japan, as per CNA.

What are the symptoms of this new variant and what is its transmissibility? Can it lead to severe cases and how worried should we be? Let’s explain.

XBB variant and its symptoms

First detected on 13 August 2022, the XBB variant is more ‘transmissible’ than the previous COVID-19 strains, experts told Singapore newspaper Today.

Dr Paul Tambyah, president of the Asia Pacific Society of Clinical Microbiology and Infection, told the newspaper, “The XBB variant is the latest of a series of variants that have emerged in countries with high vaccination rates.”

“Although we do not have all the genomic data on the current wave of cases, that (XBB being more infectious compared to other variants) is most likely the case as the number of infections has risen quite significantly over the last few weeks,” Tambyah added.

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Dr Malina Osman, Universiti Putra Malaysia epidemiologist, said the XBB variant is “one of the fastest spreading” subvariants from the Omicron lineage, as per Malaysia’s newspaper The Star.

Commenting on the symptoms of the new variant, virologist Dr Kumitaa Theva Das told The Star that the infected patients have mild symptoms such as fever and sore throat.

“Although a pre-print study stated that it is the most immune-evasive variant yet, WHO (World Health Organisation) has not declared it a variant of concern,” she was quoted as saying by the newspaper.

This strain is “probably the most immune-evasive yet," Raj Rajnarayanan, a professor at the New York Institute of Technology’s Jonesboro, Ark, told Fortune, as per News18.

XBB in India

Around 7 per cent of the new coronavirus cases in India is caused by the XBB variant, while BA.2.75 Omicron variant currently accounts for 88 per cent of the total infections, scientists involved in genome sequencing told TOI.

“The XBB is another hybrid version of Omicron. We are closely monitoring its spread in Maharashtra,” Dr Rajesh Karyakarte, state coordinator for genome sequencing was quoted as saying by TOI.

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XBB in Singapore

Nearly 55 per cent of the new COVID-19 cases in Singapore can be attributed to the XBB variant, reports CNA citing the city-state’s Ministry of Health (MOH).

Moreover, BA.5 is responsible for about 21 per cent infections and BA.2.75 comprises 24 per cent of overall cases in Singapore presently, as per PTI. Both are Omicron subvariants.  

On Tuesday, Singapore health minister Ong Ye Kung said they are ‘very closely’ monitoring the new Omicron strain.

“XBB is demonstrating characteristics that it is dominating over all other sub-variants. It has been detected in many parts of the world but in Singapore is rising very fast - within three weeks from nothing, it is now over half of all the daily cases,” the Health minister was quoted as saying by CNA.

Can XBB cause severe cases?

There is no evidence so far to suggest that the XBB variant triggers more severe infections, say experts.

Even though XBB has driven local infections in Singapore, it has not led to more severe cases, Ong Ye Kung said, as per CNA. 

Associate Professor Alex Cook, vice-dean of research at the Saw Swee Hock School of Public Health, told Today, “So far, it doesn’t seem to be leading to worse outcomes. Hospitalisation numbers are slowly going up, as we would expect with more cases, but so far, the growth in severe outcomes seems slower than the growth in cases.”

Dr Leong Hoe Nam, an infectious disease specialist at Singapore’s Mount Elizabeth Novena Hospital, told CNA that more infections will be caused due to the XBB variant because “it can outrun and dodge better than the existing strain”.

Dismissing any reason for concern, he added “severe illness numbers are not much more and within expectations”.

Which vaccine is effective?

As per experts in Singapore, the bivalent COVID-19 vaccines are expected to be “more effective than the ancestral strain-based mRNA vaccine”, reported CNA.

“The bivalent COVID-19 vaccines include a component of the original virus strain to provide broad protection against COVID-19 and a component of the Omicron variant to provide better protection against COVID-19 caused by the Omicron variant,” says the United States Food and Drug Administration.

Associate Professor Cook also said people who have not yet taken the bivalent vaccine in Singapore should get their dose.

Earlier in August, Hindustan Times had reported that Indian scientists are in discussions with domestic vaccine makers to introduce bivalent COVID-19 shots in the country.

With inputs from agencies

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