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Explainer: One week on, what we know and don't know about Omicron

The variant of concern is now in every continent but there is still much to be investigated.

Image: Alamy Stock Photo

IT’S BEEN A hell of a week for the 15th letter of the Greek alphabet. 

Seven days after the World Health Organisation (WHO) named the new Covid-19 variant of concern ‘Omicron’, the word has travelled around the world as quickly as the virus itself. 

In that time, the new variant has been identified across more than 20 countries and in all continents but much is still to be determined about exactly how concerning the new variant is. 

What do we know so far and when will we know more? 

Without repeating too much of what we’ve previously explained and what you’re likely already aware of, here are some of the basics. 

Omicron is a new variant of Covid-19 that is spreading rapidly in parts of South Africa and other parts of southern Africa. 

We don’t know for sure where it first mutated, with South African epidemiologists saying it was detected first in Botswana and then in South Africa, where the announcement of the new variant was made on 25 November.

This week, Dutch authorities announced that six days before that on 19 November an individual had tested positive for what also turned out to be the Omicron variant.

Viruses mutating is not unusual. As viruses spread, they develop mutations.

When a viral strain develops a mutation that has an advantage over other strains, such as being easier to transmit, it will likely out-compete and become the dominant strain of the virus. 

We’ve seen this happen before when the Alpha variant (unofficially referred to as the UK variant) out-competed the original variant of Covid-19 to become dominant in most places. 

Later this year the Delta variant (unofficially referred to as the India variant) became the dominant strain globally in June 2021. 

Both the Alpha and Delta variants sparked concern because they were more transmissible than the strains which came before. If a Covid strain is more transmissible it can obviously lead to more infections and could put extra pressure on health systems. 

In the case of Omicron, we cannot yet say for sure that it is more transmissible, although the early indications from tracking in South Africa suggest that it is. 

In the areas of South Africa where Omicron is growing the R number is at about 1.93, higher than 1.47 for South Africa as a whole. 

There are various reasons why that may be the case, such as age demographics, but the speed of the growth of the virus is also suggestive that Omicron is more transmissible.  

To bring some clarity to the situation, the WHO has said that it expects to be able to provide details of the transmissibility of Omicron “within days”

The primary reason for concerns about Omicron have not been related to transmissibility alone, however. 

Experts say what is particularly concerning is the number of mutations in the virus, making it the “most divergent” of the variants since the original SARS‑CoV‑2 virus that emerged in Wuhan. 

Specifically, there are several mutations to the spike protein, the area of the virus that is used to enter the body’s cells and the area on which vaccines act. 

The number of mutations could potentially mean that the variant may be better at evading the immunity responses provided by either vaccines or previous recovery from Covid. 

Again, whether or not this is the case is still being investigated.

To do this, scientists are testing blood from people who are fully immunised against a synthetic version of the Omicron variant that is grown in a lab.

Results from these tests may not be available until later next week. 

Last night, a preliminary study by South African scientists suggested that the variant was three times more likely to cause reinfection among people who previously had Covid-19. 

The study is not yet peer-reviewed but is suggestive of Omicron’s ability to evade immunity. The authors emphasised however that the study did not have information on individuals’ vaccination status and therefore could not assess to what extent Omicron evades vaccine-induced immunity.  

Other factors

Speaking in Dublin about Omicron yesterday, Taoiseach Micheál Martin said it may be two weeks before scientists have a clearer picture of three important factors relating to the variant,”how infectious it, how virulent and to what degree will the new variant escape vaccines”. 

If Omicron is sufficiently mutated to reduce vaccine effectiveness, current vaccines could adapted to better fight the virus. 

Moderna has already said it is working on an Omicron-specific vaccine, as is US rival Pfizer, with suggestions that they could be ready in 100 days

The European Medicines Agency has said it could theoretically approve the adapted vaccines in three to four months. 

“Were there a need to change the existing vaccines, we could be in a position to have those approved within three to four months,” the EMA’s Emer Cooke told a European Parliament committee. 

The other question that needs to be answered is whether Omicron is more or less virulent than previous strains, i.e. whether it leads  to more or less severe disease.   

Again, it is too soon to draw any conclusions on this. 

On Sunday, a South African doctor said she had treated about 30 cases of Omicron and had only encountered “mild symptoms” in these patients.

The scientific community has warned against drawing conclusions based on this testimony because the patients were mostly young and therefore less at risk of serious Covid.

In fact, as most people are aware after almost two years into this pandemic, the  Covid cases are indeed mild in the vast majority of people. 

The fact that some Omicron cases are almost mild is merely reflective of this fact. 

Speaking this week, the WHO’s Dr Maria Van Kerkhove said they have seen reports of Omicron cases which “go from mild disease all the way to severe disease”. 

If Omicron turns out to be more transmissible and of similar or greater severity than previous strains than this would be bad news, but if it were the case Omicron was more transmissible but milder this would of course potentially be good news.   

How widespread is Omicron?

Omicron has been confirmed in over 20 countries and counting, but the question as to whether it will overtake Delta as the dominant global strain remains to be seen. 

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Previous Covid variants such Mu and Lambda did not manage to overtake Delta but the spread of Omicron in the Gauteng province in South Africa suggests it could.

Yesterday, the European Centre for Disease Control (ECDC) said that if the pattern in South Africa is reproduced in Europe, Omicron could make up the majority of Covid cases within a few months.

However, Delta was never very present in South Africa, so a comparison with Europe is hard to draw at this stage. 

In Scotland, there has been some evidence of community transmission where 13 Omicron cases have been confirmed, some of which had no link to travel or other cases. 

Ireland confirmed its first case of Omicron on Wednesday, in a person who had last week travelled from southern Africa. 

Dr Cillian De Gascun of the National Virus Reference Laboratory said in a technical briefing that there were was ”no evidence” yet of community transmission in this country. 

He said that for Omicron to become dominant in Ireland the variant must have a transmission advantage and socialisation for this advantage to play out.  

If this were to happen, De Gascun said that “generally speaking” this might happen over roughly 4-8 weeks, but that again this is uncertain. 

“We still don’t really have as much definitive evidence of its transmission advantage, although the data from South Africa is certainly suggestive,” he said. 

What we know from previous experiences is if a variant gets into the country over a period of time and reaches a certain level, ultimately there will be a tipping point at which stage it will begin to become dominant and generally speaking this takes place over a period of 4-8 weeks.

“Obviously it has to reach that critical mass first, it has to get out into the community and there has to be a level of community transmission and at the moment we don’t see any evidence at least of community transmission of this variant in Ireland.”

About the author:

Rónán Duffy

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