New Covid variant spreading in the UK – What do you need to know about Omicron BA.4.6

COVID-19 was first reported in December 2019 – almost three years and several variants later, a new type in Omicron BA.4.6 is emerging.

One thing’s for sure about SARS-CoV-2, the virus that causes COVID-19 is constantly changing. Since the start of the pandemic, there have been some prominent variants, including Alpha, Beta, Delta and Omicron [1]. 

Previous COVID-19 variants

Alpha (B.1.1.7): the first of the highly publicised variants, Alpha first emerged in Great Britain in November 2020. Infections rose in December of the same year. 

It soon appeared worldwide and evolved into the prevalent variant in the US, where the CDC categorised it as a variant of concern. Then, Alpha waned away with the rise of the more aggressive Delta.

Beta (B.1.351): this variant was identified in South Africa at the end of 2020 and dispersed to other countries. Experts had been troubled about its several mutations and the possibility of evading antibodies. Beta was not usual in the US.

Delta (B.1.617.2): this was first identified in India in late 2020 and shortly spread through the world, turning into what was the predominant version of the coronavirus until Omicron took its place in mid-December. 

Delta (AY.4.2): periodically referred to as Delta Plus, it was the most well-known of several Delta results, some of which had mutations new to Delta but were seen in other variants. 

AY.4.2 had a couple of mutations to its spike protein, AY145H and A222V, that were considered critical, but they were not located where they would interfere with treatments or vaccunes. This particular variant was thought to be slightly more contagious than Delta – while the UK was seeing a steady rise of AY4.2, it did not increase as fast in the US.

Omicron and its subvariants: the earliest Omicron strain (BA.1) was initially seen in South Africa and Botswana in late November 2021, and cases quickly started to appear and multiply in other countries. By December, Omicron was pushing daily case numbers in the US to rocket to over a million. 

At the end of August 2022, one of those subvariants, BA.5, made up more than 88 per cent of cases in the United States, making it the dominant variant in this country. A related variant, BA.4, was also advancing, making up about 8 per cent of cases. 

the earliest Omicron strain (BA.1) was initially seen in South Africa and Botswana in late November 2021, and cases quickly started to appear and multiply in other countries.

What’s currently known about Omicron BA.4.6

New COVID-19 variant BA.4.6 now accounts for more than 9 per cent of recent cases across the US. The variant has also been pinpointed in several other countries [2]. 

Here’s what’s known about the latest variant so far [3]:

  • As omicron infections are usually less severe than earlier variants, the same is expected of the subvariant BA.4.6.
  • As omicron subvariants, BA.4.6 is also more infectious, a yet-to-be peer-reviewed study noted.
  • BA.4.6 is a descendant of the BA.4 variant of omicron, which was first detected in January 2022 in South Africa.
  • The subvariant could be recombinant.
  • The subvariant is similar to BA.4 as it carries a mutation- R346T- to the spike protein.
  • UK health agency indicated that the subvariant BA.4.6 reproduces more quickly in the early phases of infection. 

Vaccination is strongly recommended

The inception of BA.4.6 and other new variants is unsettling. It demonstrates the virus is still very much with us and is mutating to find new ways to overpower our immune response from vaccination and previous infections [4].

We know people who previously had COVID can contract the virus again, remarkably accurate to Omicron. In some cases, succeeding episodes can be worse [5].

Vaccination continues to deliver good protection against severe diseases and is still the most suitable weapon we have to fight COVID-19. The recent authorisation of bivalent boosters is promising news. Beyond this, developing multivalent coronavirus vaccines that target multiple variants could administer even more durable protection [6].

The inception of BA.4.6 and other new variants is unsettling

A recent study showed that a multivalent coronavirus vaccine given through the nose elicited a solid immune response against the primary strain of SARS-CoV-2 and two variants of concern in mouse models [7].

Close monitoring of new variants, including BA.4.6 is encouraging, as they could guide the next wave of the COVID pandemic. For the public it will pay to remain cautious and comply with any public health measures to control the spreading of what remains a very contagious virus.

Expected booster vaccination side effects

In Pfizer and Moderna’s clinical trials for the BA.1 shots, individuals who were already fully vaccinated with a booster shot acquired an updated booster dose. In both clinical trials, the most typically reported side effects within a week of receiving the shot were [89]:

  • Chills 
  • Fatigue
  • Fever
  • Headache
  • Joint pain
  • Muscle pain 
  • Pain
  • Redness and swelling at the injection site

It’s the same group of side effects that came with the original formulations. But notably, in those clinical trials, the severity of the side effects was very mild.

Pfizer’s trial found that about 52 per cent of participants that received the BA.1 shot experienced mild pain at the injection site, 8 per cent experienced moderate pain and only 0.3 per cent experienced severe pain. Roughly 26 per cent of individuals had a mild or moderate headache, while only 0.3 per cent experienced a severe one.

Moderna’s trial found that nearly 59 per cent of participants experienced fatigue, but only about 4 per cent experienced that at a Grade 3 level, defined as significant fatigue that prevents daily activity.

Severe side effects are “generally” most common after receiving a second dose of a vaccine, not after a third or fourth dose. You’re only eligible for the new boosters if you’ve completed a primary vaccination series – meaning most people will have already received at least two doses ahead of time.

The same concept was true for the last booster shots [10]. The new shots have the same dosage amounts as the original vaccines, suggesting that their safety profiles could be similar.

A single dose of Pfizer’s monovalent vaccine contains 30 micrograms of mRNA targeting the original Covid strain. The updated booster shots have the same number of micrograms, with 15 targeting the original strain and the other 15 targeting BA.4 and BA.5.

Moderna’s monovalent shot contains 50 micrograms of mRNA per dose targeting the original strain. Its updated booster has 25 micrograms targeting the original strain, and 25 targeting the omicron subvariants [11]. The BA.1 trials exclusively tested a few hundred people, a rather small sample size likened to the thousands of Americans set to receive the new BA.5 doses.


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