WASHINGTON.-BA.4.6, a sub-variant of the omicron COVID variant that is rapidly gaining traction in the US, has now been confirmed to be spreading in the UK.
The latest UK Health Safety Agency (UKHSA) briefing paper noted that for the week starting August 14, BA.4.6 accounted for 3.3% of UK samples. It has since grown to account for about 9% of sequenced cases.
Similarly, according to the Centers for Disease Control and Prevention, BA.4.6 now accounts for more than 9% of recent cases in the US. The variant has also been identified in several other countries around the world.
So what do we know about BA.4.6? We must worry? Let’s take a look at the information we have so far.
The BA.4.6 is a descendant of omicron’s BA.4 variant. The BA.4 was first unveiled in January 2022 in South Africa and has since spread worldwide along with the variant BA.5.
It is not entirely clear how BA.4.6 arose, but it is possible that it is 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 be similar to BA.4 in many ways, it carries a mutation in the spike protein, a protein on the surface of the virus that allows it to enter our cells. this mutation, R346Tis seen in other variants and is associated with immune evasion, meaning it helps the virus escape antibodies acquired from vaccination and previous infection.
Burden, infectivity and immune evasion
Fortunately, Omicron infections usually cause illness less severe and we saw fewer deaths with omicron compared to previous variants. We expect this to also apply to BA.4.6. In fact, there are no reports of this variant yet causes more severe symptoms.
But we also know that omicron subvariants tend to be more contagious than the previous options. BA.4.6 seems even better for avoid 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 Although this information is based on a preprint (a study that has not yet been peer-reviewed), other emerging data support it.
According to the UKHSA report, early estimates show that BA.4.6 has a 6.55% relative fitness advantage over BA.5 in England. This shows 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 is 45% to 55%.
The University of Oxford reported that people who received three doses of Pfizer’s original COVID vaccine produced fewer antibodies in response to BA.4.6 than BA.4 or BA.5. This is alarming because it suggests that the vaccines against COVID may be less effective against BA.4.6.
However, the ability of BA.4.6 to evade immunity can be addressed to some extent by new bivalent boosters that specifically target omicron along with the SARS-CoV-2 parent strain. Time will tell.
Meanwhile, a preliminary study shows that BA.4.6 evades the protection of evusheldantibody therapy designed to protect people who are immunosuppressed and who do not respond well to COVID vaccines.
Vaccination is key
The appearance of BA.4.6 and other new variants is worrying. This shows that the virus is still with us and is mutating to find new ways to overcome our immune response from vaccination and previous infections.
We know that people who have had COVID before can get the virus again, and this is especially true for omicron. In some cases, subsequent episodes may be worse.
But vaccination continues to offer a good protection against serious illness and remains the best weapon we have to fight COVID. The recent approval of divalent boosters is good news. In addition, the development of multivalent coronavirus vaccines that target multiple variants may provide even longer-lasting protection.
A recent study showed that a multivalent coronavirus vaccine administered intranasally induced a strong immune response against the parent strain of SARS-CoV-2, as well as two worrisome variants, in mouse models.
Close monitoring of new variants, including BA.4.6, is urgently needed as they may lead to the next wave of the COVID pandemic. It will be worthwhile for the public to remain cautious and adhere to public health measures to prevent the spread of what remains a highly contagious virus.
Original article published by The Conversation