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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.

BA.4.6 is a descendant of the BA.4 variant of omicron. BA.4 was first detected in Jan 2022 in South Africa and has since spread around the world alongside the BA.5 variant.

It is not clear how BA.4.6 has emerged, but it's possible it could be a recombinant variant. Recombination happens when two different variants of SARS-CoV-2 infect the same person, at the same time.

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.

Omicron infections generally cause less serious illness, and we've seen fewer deaths with omicron. We would expect this to apply to BA.4.6 too.

We also know that omicron subvariants tend to be more transmissible than previous variants.

BA.4.6 replicates more quickly in the early stages of infection and has a higher growth rate than BA.5.

Vaccination continues to offer good protection against severe disease, and is still the best weapon we have to fight COVID. So, stay cautious and comply with health measures.