The new COVID subvariant BA.4.6 is spreading. Here’s what we know: ScienceAlert

BA.4.6, a sub-variant of the Omicron COVID variant that has quickly gained traction in the US, has now been 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 percent of samples in the UK. It has since grown to make up around 9 percent of sequenced cases.

Similarly, according to the Centers for Disease Control and Prevention, BA.4.6 now accounts for more than 9 percent of recent cases across the United States. 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 concerned? Let’s take a look at the information we have so far.

The BA.4.6 is a descendant of the BA.4 variant of Omicron. The BA.4 was first discovered in January 2022 in South Africa and has since spread worldwide along with the BA.5 variant.

It is not entirely clear how BA.4.6 arose, but it is possible that it could be a recombinant variant. Recombination occurs 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 resemble BA.4 in many ways, it carries a mutation to the spike protein, a protein on the surface of the virus that 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 escape antibodies from vaccination and previous infection.

Severity, infectiousness and immune evasion

Fortunately, Omicron infections generally cause less severe illness, and we have seen fewer deaths with Omicron than with previous variants. We expect this to also apply to BA.4.6. In fact, there have been no reports yet of this variant causing more severe symptoms.

But we also know that Omicron subvariants tend to be more transferable than earlier 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 Although this information is based on a preprint (a study that has not yet been peer-reviewed), other new data support this.

According to UKHSA’s briefing, early estimates suggest that BA.4.6 has a relative fitness advantage of 6.55 per cent over BA.5 in England. This indicates that BA.4.6 replicates faster in the early stages of infection and has a higher growth rate than BA.5.

The relative fitness advantage of BA.4.6 is significantly less than that of BA.5 over BA.2, which was 45 percent to 55 percent.

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 of concern because it suggests that COVID vaccines may be less effective against BA.4.6.

However, the capacity of BA.4.6 to escape immunity can be addressed to some extent by the new bivalent boosters, which specifically target Omicron, together with the original strain of SARS-CoV-2. Time will tell.

Meanwhile, a preprint study shows that BA.4.6 evades protection from Evusheld, an antibody therapy designed to protect people who are immunocompromised and do not respond as well to Covid vaccines.

Vaccination is key

The emergence of BA.4.6 and other new variants is worrying. It shows that the virus is still very much with us, mutating to find new ways to overcome our immune response from vaccination and previous infections.

We know that people who have had COVID in the past can get the virus again, and this has been particularly the case for Omicron. In some cases, subsequent episodes may be worse.

But vaccination still provides good protection against serious illness, and is still the best weapon we have to fight COVID. The recent approval of bivalent boosters is good news. In addition, the development of multivalent coronavirus vaccines that target multiple variants may provide even more durable protection.

A recent study showed that a multivalent coronavirus vaccine administered through the nose elicited a strong immune response against the original strain of SARS-CoV-2, as well as two variants of concern, in mouse models.

Close monitoring of new variants including BA.4.6 is urgent as they may lead to the next wave of the COVID pandemic. For the public, it will pay to be cautious and observe all public health measures in place to prevent the spread of what is still a highly contagious virus.The conversation

Manal Mohammed, Senior Lecturer, Medical Microbiology, University of Westminster

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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