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Omicron vs Delta: how is the new variant different?

CANMORE, ALTA. – Scientists around the world are rushing to learn more about the recently discovered B.1.1.529 variant of the coronavirus, now known as Omicron, to see how it compares to other worrisome variants.

Important questions – like its degree of communicability, its ability to evade immunity to vaccines or past illnesses, and whether it causes more serious illness – remain unanswered.

While some scientists say it will be weeks before we have a clear picture of Omicron’s impact on the pandemic, the World Health Organization (WHO) said on Wednesday it expects to have more information on the transmissibility of the variant in a few days.

What we do know about this variant is that it contains over 30 mutations in the spike protein, which allows it to bind to human cells and enter the body – a factor that has caused great concern. for some scientists.


First of all, it’s important to remember that mutations in SARS-CoV-2, the virus that causes COVID-19, have been expected since the early days of the pandemic. This is because mutations always occur as viruses spread – this is how they ensure their own survival.

According to researchers at Yale University, SARS-CoV-2 accesses our cells using its “crown” – a layer of protein spikes that fit into our cells like a lock and key – where it does. copies of its genomes.

But during this process, errors are inevitably introduced into the code, causing a mutation or variant.

Sometimes these mutations are harmless. But other times, as in the case of the Delta variant, the virus may change to become more transmissible or cause more serious illness.

“What we’ve seen with other viruses is that over time they mutate in various ways. And one of the ways they can mutate is to get a little less severe because the virus comes at a small cost to fitness, ”said Dr. Susy Hota, infectious disease expert at the University of Toronto Health Network, to Your Morning Wednesday on CTV.

“If he starts killing his hosts a little too early, he just won’t fight back.” And that’s the purpose of a virus is to make more copies of itself and persist over time.

Hota notes that COVID-19 has retained its advantage with previous variants, as it tends to have infections that last quite a long time, giving it plenty of scope to spread from person to person.


The variant genome, in total, contains around 50 mutations, including those in the spike protein, according to the British Medical Journal (BMJ). Scientists say it did not directly evolve from the Delta variant and contains characteristic changes found in the Alpha, Beta, Gamma, and Delta variants.

“This variant carries some changes that we’ve seen previously in other variants, but never completely in a virus. It also contains new mutations that we’ve never seen before, ”Lawrence Young, virologist and professor of molecular oncology at Warwick Medical School, told BMJ in a briefing released Monday.

Another distinctive note is that one of Omicron’s mutations leads to “S gene target failure” – also known as “S gene dropout” – meaning that one of the many areas of the gene targeted by PCR tests gives a false negative.

“In a PCR test, three different genes are monitored. However, one of the S gene targets goes undetected due to the mutations, ”said Chris Richardson, professor of microbiology and immunology at Dalhousie University, in a statement released Tuesday.

“This is called S gene drop or S gene target failure, which is actually useful and diagnoses omicron. Stall is a marker for this variant.

According to the World Health Organization (WHO), Omicron has been detected at faster rates than previous outbreaks of infection using this approach.

But researchers in South Africa first sounded the alarm on the B.1.1.529 variant after finding more than 30 mutations in the spike protein – a number much higher than what we’ve seen with n any other variant.

Since the spike protein is the target of the antibodies our immune system produces to fight COVID-19, a high number of mutations raises concerns that Omicron may escape antibodies produced by a previous COVID-19 infection or vaccination. .

“The spike protein of the virus is really important for entry into cells, as well as targets for antibodies that help control infections. It is therefore possible, scientifically, by looking at the virus that it is more transmissible than what we have seen so far, ”explained Hota.

“It could also lead to what we call immune breakout – in other words, your immune system may not be able to control it as well, so you may be susceptible to more re-infections or maybe vaccines. a little less effective. “

But Hota says these are just assumptions and we need to be careful not to draw any conclusions from speculation or anecdotal reports about the severity of the disease or Omicron’s transmissibility at this point.

“I think we need to see it in more people to get a good idea of ​​how it compares to what we’ve seen so far with COVID 19,” she said.


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