Another new COVID variant is spreading: What we know about omicron BA.4.6

BA.4.6, a subvariant of the omicron COVID variant which has been quickly gaining tractionin the U.S., is now confirmed to be spreadingin the U.K.

Thelatest briefing documenton COVID variants from the U.K. Health Security Agency (UKHSA) noted that during the week beginning August 14, BA.4.6 accounted for 3.3% of samples in the U.K. It has since grown to make up around 9% of sequenced cases.

Similarly, according to the Centers for Disease Control and Prevention, BA.4.6 now accounts formore than 9%of recent cases across the U.S. Thevarianthas also been identified inseveral other countriesaround the world.

So what do we know about BA.4.6, and should we be worried? Let's take a look at the information we have so far.

BA.4.6是一个后代of the BA.4 variant of omicron. BA.4 wasfirst detectedin January 2022in South Africaand has since spreadaround the worldalongside theBA.5 variant.

It is not entirely clear how BA.4.6 has emerged, but it's possible it could be arecombinant 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 seenin other variantsand is associated withimmune evasion, meaning 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 seenfewer deathswith omicron than with earlier variants. We would expect this to apply to BA.4.6 too. Indeed, there have been no reports yet that this variant is causing moresevere symptoms.

But we also know that omicron subvariants tend to bemore transmissiblethan previous variants. BA.4.6 appears to beeven better在逃避immune systemthan BA.5, the currently dominant variant. Although this information is based ona preprint(a study that is yet to be peer-reviewed), other emerging data supports this.

According tothe UKHSA's briefing, early estimates suggest BA.4.6 has a 6.55% relative fitness advantage over BA.5 in England. This indicates that BA.4.6 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 isconsiderably smallerthan that of BA.5 over BA.2, which was 45% to 55%.

The University of Oxfordhas reportedthat 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 boosters, which target omicron specifically, alongside the original strain of SARS-CoV-2. Time will tell.

Meanwhile, onepreprint studyshows that BA.4.6 evades protection fromEvusheld, an antibody therapy designed to protect people who are immunocompromised anddon't respond as wellto COVID vaccines.

Vaccination is key

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 fromvaccinationand previous infections.

We know people who have had COVID previously can contract the virusagain, and this has been particularly true ofomicron. In some cases, subsequent episodes can be worse.

但接种疫苗continues to offer good protection againstsevere disease, and is still the best weapon we have to fight COVID. The recent approval of bivalent boosters is good news. Beyond this, developingmultivalent coronavirus vaccinesthat target multiple variants could provide even more durable protection.

Arecent studyshowed that a multivalent coronavirus vaccine administered through the nose elicited a strongimmune responseagainst 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 pressing, as they could lead to the next wave of COVID pandemic. For the public, it will pay to stay cautious, and comply with anypublic health measuresin place to prevent the spread of what remains a very contagious virus.

This article is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.