A s🐽ubvariant of the Omicron Covid variant, BA.4.6 has been quickly gaining traction in the US and now it is fast spreading in the United Kingdom. Close monitoring of new variants including BA.4.6 is pressing, as they could lead to the next wave of Covid pandemic.
Th▨e 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 pe🥃r cent of sequenced cas🔯es.
Similarly, 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.
So what do we know about BA.4.6, and should we be worried?
BA.4.6 is a descendant of the 𒀰BA.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 is not entirely 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 (the virus that causes Covid-19) infect the same person, at the same time.
How infectious is it?
While BA.4.6 will be 𝔍similar 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, meꦕaning it helps the virus to escape antibodies acquired from vaccination and prior infection🌞.
Severity, infectiousness and immune evasion. Fortunately, omicron infections generally cause less serious illness, and we've seen fewer deaths with omicron than with earlier variants. We would expect this to apply to BA.4.6 too. Indeed, there have been no reports yet that th💎is variant is causing more severe symptoms.
But 🍌we also know that🔴 omicron subvariants tend to be more transmissible than previous variants.
BA.4.6 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 stud𒀰y that is yet to be peer-reviewed), other emerging data supports this.
According to the UKHSA's bꦅriefing, early estimates suggest BA.4.6 has a 6.55 per cent relative fitness advantage o🔯ver BA.5 in England.
This indicates that BA.4.6 replicates more quickly in the early stages of infection and has a higher growth ꦰrꦡate 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.
How will vaccination help?
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.
The capacity of BA.4.6 to evade immunity may however be addressed to a degree by the new bivalent ♏booste🔯rs, which target omicron specifically, alongside the original strain of SARS-CoV-2. Time will tell.
Meanwhile, one preprint study shows that BA.4.6 evades protection from Evusheld, an antib𒈔ody 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. I🌞t shows the virus is still very much with us, and is mutating to find new ways to overcome our immune response from vaccination an✱d previous infections.
We know people who have had Covid previously can contract the virus again, and this has been particularly true of omicron. In some cases, subsequent episodes c🥂an be worse.
But vaccination continues to offer good protection against severe disease and is still the best weapon we have to fight Covid. The recent approval of bivalent boosters is good news. Beyond this, developing multivalent co⛎ronavirus vaccines that target multiple variants could provide even more durable protection.
A recent study showed that a multivalent coronavirus vaccine admi🌱nistered through the nose elicited a st💝rong immune response against the original strain of SARS-CoV-2, as well as two variants of concern, in mouse models.
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.
(with PTI inputs)
