Omicron sub-variant XBB.1.5 explained — transmissibility, severity, immune evasive effects and more

India has so far reported seven XBB.1.5 variant cases, according to the data released by the Indian SARS-CoV-2 Genomics Consortium (INSACOG) on Thursday. As per the information, these seven were identified in Gujarat, Karnataka, Telangana, Chhattisgarh and Rajasthan.

This XBB.1.5 Omicron is dominant in the United States (ST) and is said to be responsible for the rise in cases there. Combined, XBB and XBB.1.5 make up 44 percent of cases in the US as of now, PTI reports.

The World Health Organization (WHO) recently highlighted that this XBB.1.5 variant is the "most transmissible sub-variant that has been recorded yet", said WHO epidemiologist Maria Van Kerkhove.

Now that seven cases of this variant have been reported in India, how worried should the country be — in terms of the surge in cases, deaths, hospitalisations, vaccination and severity?

Virologist Gagandeep Kang says she does not expect a surge in India, noting that "XBB and BF.7 for a while and they have not driven an upsurge in India. In the absence of an even more highly infectious variant, I do not expect a surge."

She mentions "hybrid" immunity among Indians as another reason to rule out the surge. Hybrid immunity is achieved by a person if he or she had been infected with the virus and has also been vaccinated.

While WHO expects "further waves of infections around the world", Kerkhove says "it does not have to necessarily translate into further waves of death."

Yes, it can, as noted by WHO's Kerkhove. She said, "It (XBB.1.5) is replacing other sub-variants in some countries and has "immune escape like XBB".

There are chances that people with prior infection or even those vaccinated against the coronavirus can get infected with XBB.1.5 Omicron variant.

"Immune evasiveness is the ability of the virus to infect people who had prior infection or vaccination or both. XBB.1.5 achieved this by creating a rare type of mutation...," Dr Rajeev Jayadevan, Co-chairman of the National IMA Covid task force, was quoted by ANI as saying.

Moreover, according to a CNBC report, scientists said that XBB.1.5 is as good as XBB and XBB.1 at dodging antibodies from vaccines and infection.

But, current vaccines continue to protect against severe symptoms, hospitalisation and death, Reuters quoted experts as saying.

Dr Chandrakant Lahariya, a leading public health and policy expert, don't believe that a "healthy adult need a booster dose". He had earlier told CNBCTV-18.com : "There's a global evidence that while the third shot provides some benefit, the fourth shot has marginal benefits."

Meanwhile, Kang said in a tweet posted on December 23, "Two doses of any vaccine protect against severe disease/deaths." She further noted that "...from the rest of the world, the value of a booster in the elderly population is clear".

Experts believe it is unlikely to do so. The WHO epidemiologist said the world health body does not have any data on the severity of the variant so far. But "we don't have any indication that the severity has changed", she added. But, increased transmissibility is always a concern.

The WHO was unable to attribute the increase in hospitalisations in the northeastern US to the variant. However, a month back, American epidemiologist Eric Feigl-Ding had warned that "super variant" XBB.1.5 is behind "hospitalisation surges in New York/New England".

The XBB.1.5 strain is a relative of the Omicron XBB variant — which is a recombinant of the Omicron BA.2.10.1 and BA.2.75 subvariants.

The WHO says, "One of the Omicron sub-variants originally detected in October 2022 is XBB.1.5. It is on the increase in the US and Europe and has now been identified in more than 25 countries".

The INSACOG data also showed that seven cases of BF.7 strain, which is driving China's COVID-19 wave, have been found in India. There are four cases of Omicron sub-variant BF.7 reported in West Bengal, two in Gujarat and one in Odisha.