Fast-moving variants of Omicron are being reported – more so in Maharashtra. What are these Covid sub- variants?

Omicron sub-variants XBB, BQ.1 have been reported. XBB is a recombinant (combination) of two Omicron BA.2 sub-variants (BA.2.10.1 and BA.2.75). A lot of mutations on the surface of the virus is responsible for the immune escape from neutralising antibodies targetting the spike protein. According to WHO (as of October 12, 2022), Omicron is currently the dominant variant circulating globally accounting for over 98 per cent of sequences shared on GISAID since February.

Where else has this Covid sub-variant been reported in India and worldwide. Was it detected first here?

According to the WHO weekly epidemiology update on COVID-19 (October 26,2022), 390 Omicron-descendent lineages and 48 recombinants have been identified. XBB and XBB.1 have been reported by 35 countries with 1,453 genomic sequences, including Singapore, India, Bangladesh, Australia and USA. It has been associated with a surge in COVID-19 in Singapore, although cases have started to decline since last week.

Is it a cause of concern? Does it have a potential to trigger a surge?

Like other viruses, the SARS-CoV2 virus is expected to mutate and change over a period of time. Some of these mutations may not be significant but changes – according to the WHO – can affect the virus’s properties, like how easily it can spread and the related disease severity.

XBB sub-variant is perhaps the most immune-evasive variant till date, especially for escaping neutralising antibody responses induced by vaccinations or previous infections. This can lead to an increase in infections. However, there is no data about it being associated with more severe illness. Based on the Singapore experience, it seems vaccines may work well in preventing severe illness associated with this sub-variant. Resistance to monoclonal antibodies that prevent progression to severe illness in high-risk individuals has also been noted with this sub-variant.

What are the number of cases and symptoms so far?

XBB and XBB.1 have been reported by 35 countries with 1,453 genomic sequences. Because of immune evasion properties, re-infections and breakthrough infections can occur but are mostly mild, causing upper respiratory symptoms.

What about vaccine effectiveness?

Very preliminary evidence suggests vaccines may be holding up in preventing severe illness. Further information is expected from the statement of the WHO Technical Advisory Group on Viral Evolution that will be released soon.

There is Covid fatigue. With so many new sub-variants, should people take a booster? What about an mRNA one?

Yes, people should take a booster since they may still be useful in preventing severe illness and hospitalisation. Vaccines (including precaution doses) may help in preventing severe illness. Hence taking boosters are important, especially for individuals with high risk for severe illness. As of now mRNA vaccines are not available in India.

What precautionary measures should be taken?

Precaution dose catch-up is essential for the elderly, especially those with chronic co-morbidities and immune suppression. Masking needs to continue especially in closed, congregated settings without adequate ventilation. Staying home when sick with acute respiratory illness is also important. Increased surveillance, including genomic sequencing, needs to continue.

Why Dr Pujari

Dr Sanjay Pujari, MD, FIDSA, is Director and Chief Consultant at the Institute of Infectious Diseases, Pune. He is also member of the Indian Council of Medical Research (ICMR)-Covid 19 task force