Omicron XBB.1.5 variant highly transmissible and infectious, Lancet study shows

Jumpei Ito from the varsity’s Division of Systems Virology said, “Our data suggest that XBB.1.5 will rapidly spread worldwide in the near future.”

Earlier in January, Omicron XBB.1.5 strain was the fast spreading strain across the globe. Countries like US, Britain were dominated by this strain. India too saw COVID’s XBB.1.5 strain in the country. 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. 

In January, World Health Organisation (WHO) had revised the risk assessment for Omicron XBB.1.5 variant from “Low” to “Moderate”. WHO had noted that the variant was likely to contribute to increase in case incidence globally and had also mentioned that ‘number of cases associated with XBB.1.5 was low and thus severity cannot yet be confidently assessed. 

Speaking of symptoms, XBB.1.5 led COVID infections were having same impact on people as the previous variants were. Classic COVID symptoms like runny nose, sore throat, headache are seen in patients reporting positive for COVID. Experts had added that XBB.1.5 are more likely to report flu-like symptoms like feeling very sick in general due to the high fevers.

Also Read: Suffering from fever and cough? How do you know its H3N2 or new COVID variant XBB 1.16

Coming back to the study, Prof. Kei Sato from the Division of Systems Virology said that XBB.1.5 has potential to cause the next epidemic surge. He further added that the variant needs to be carefully monitored “to safeguard public health”.

While studying emerging variants of the SARs-CoV-2 Omicron lineage, the research team found that the SARS-CoV-2 Omicron XBB.1.5 variant has a novel mutation in the spike (S) protein—the protein that anchors the virus firmly to the human angiotensin converting enzyme-2 (ACE2) receptor, thus facilitating the invasion of human cells.

Further experiments using lentivirus-based pseudoviruses also showed that XBB.1.5 had approximately 3-fold higher infectivity than XBB.1. The study also led to another important discovery from an immunization perspective which is the XBB.1.5 S protein was found to be highly resistant to neutralization antibodies elicited by breakthrough infection with the BA.2/BA.5 subvariants.

In other words, patients with prior infection from the BA.2/BA.5 subvariants may not show robust immunity against XBB.1.5, increasing their chances of infection and disease, the study showed.

Yusuke Kosugi from the Division of Systems Virology, Department of Microbiology and Immunology, “The results of our virological experiments explain why the Omicron XBB.1.5 variant has a higher transmissibility than past variants: This variant acquired strong binding ability to human ACE2 while maintaining a higher ability to escape from neutralizing antibodies.

Jumpei Ito from the varsity’s Division of Systems Virology said, “Our data suggest that XBB.1.5 will rapidly spread worldwide in the near future.”

Earlier in January, Omicron XBB.1.5 strain was the fast spreading strain across the globe. Countries like US, Britain were dominated by this strain. India too saw COVID’s XBB.1.5 strain in the country. 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. 

In January, World Health Organisation (WHO) had revised the risk assessment for Omicron XBB.1.5 variant from “Low” to “Moderate”. WHO had noted that the variant was likely to contribute to increase in case incidence globally and had also mentioned that ‘number of cases associated with XBB.1.5 was low and thus severity cannot yet be confidently assessed. 

Speaking of symptoms, XBB.1.5 led COVID infections were having same impact on people as the previous variants were. Classic COVID symptoms like runny nose, sore throat, headache are seen in patients reporting positive for COVID. Experts had added that XBB.1.5 are more likely to report flu-like symptoms like feeling very sick in general due to the high fevers.

Also Read: Suffering from fever and cough? How do you know its H3N2 or new COVID variant XBB 1.16

Coming back to the study, Prof. Kei Sato from the Division of Systems Virology said that XBB.1.5 has potential to cause the next epidemic surge. He further added that the variant needs to be carefully monitored “to safeguard public health”.

While studying emerging variants of the SARs-CoV-2 Omicron lineage, the research team found that the SARS-CoV-2 Omicron XBB.1.5 variant has a novel mutation in the spike (S) protein—the protein that anchors the virus firmly to the human angiotensin converting enzyme-2 (ACE2) receptor, thus facilitating the invasion of human cells.

Further experiments using lentivirus-based pseudoviruses also showed that XBB.1.5 had approximately 3-fold higher infectivity than XBB.1. The study also led to another important discovery from an immunization perspective which is the XBB.1.5 S protein was found to be highly resistant to neutralization antibodies elicited by breakthrough infection with the BA.2/BA.5 subvariants.

In other words, patients with prior infection from the BA.2/BA.5 subvariants may not show robust immunity against XBB.1.5, increasing their chances of infection and disease, the study showed.

Yusuke Kosugi from the Division of Systems Virology, Department of Microbiology and Immunology, “The results of our virological experiments explain why the Omicron XBB.1.5 variant has a higher transmissibility than past variants: This variant acquired strong binding ability to human ACE2 while maintaining a higher ability to escape from neutralizing antibodies.