New Delhi: BA.4.6, a subvariant of the omicron COVID variant which has been quickly gaining traction in the US, is now confirmed to be spreading in the UK. The latest briefing document on COVID variants from the UK Health Security Agency (UKHSA) noted that during the week beginning August 14, BA.4.6 accounted for 3.3 per cent of samples in the UK. It has since grown to make up around 9 per cent of sequenced cases, news agency PTI reported.
According to the Centres for Disease Control and Prevention, BA.4.6 now accounts for more than 9 per cent of recent cases across the US. The variant has also been identified in several other countries around the world.
What is BA.4.6 variant?
- It is a descendant of the BA.4 variant of omicron. BA.4 was first detected in January 2022 in South Africa and has since spread around the world alongside the BA.5 variant.
- It could be a recombinant variant. Recombination happens when two different variants of SARS-CoV-2 (the virus that causes Covid-19) infect the same person, at the same time.
- While BA.4.6 will be similar to BA.4 in many ways, it carries a mutation to the spike protein, a protein on the surface of the virus which allows it to enter our cells.
- This mutation, R346T, has been seen in other variants and is associated with immune evasion, meaning it helps the virus to escape antibodies acquired from vaccination and prior infection.
- It appears to be even better at evading the immune system than BA.5, the currently dominant variant. Although this information is based on a preprint (a study that is yet to be peer-reviewed), other emerging data supports this.
- It replicates more quickly in the early stages of infection and has a higher growth rate than BA.5.
- The relative fitness advantage of BA.4.6 is considerably smaller than that of BA.5 over BA.2, which was 45 per cent to 55 per cent.
- The University of Oxford has reported that people who had received three doses of Pfizer’s original Covid vaccine produce fewer antibodies in response to BA.4.6 than to BA.4 or BA.5. This is worrying because it suggests that Covid vaccines might be less effective against BA.4.6.
- One preprint study shows that BA.4.6 evades protection from Evusheld, an antibody therapy designed to protect people who are immuno-compromised and don’t respond as well to Covid vaccines.
The emergence of BA.4.6 and other new variants is concerning. It shows the virus is still very much with us, and is mutating to find new ways to overcome our immune response from vaccination and previous infections. People who have had COVID previously can contract the virus again, and this has been particularly true of omicron. In some cases, subsequent episodes can be worse.
Close monitoring of new variants including BA.4.6 is pressing, as they could lead to the next wave of COVID pandemic, the report said, adding that for the public, it will pay to stay cautious, and comply with any public health measures in place to prevent the spread of what remains a very contagious virus.
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