Omicron variant: What we know, what we don’t on symptoms, transmission, and vaccines

Simone McCarthy, South China Morning Post

Posted at Dec 01 2021 02:07 PM | Updated as of Dec 01 2021 02:15 PM

The new coronavirus variant Omicron has put the world on high alert, with health officials warning of possible case surges and pressure on hospitals, even as scientists scramble to understand this highly mutated strain.

The World Health Organization has flagged the variant – reported to the health agency last week – as “very high” risk. Preliminary evidence suggests that Omicron could dodge immune defences and spread more readily than earlier strains, according to the WHO.

But the agency has also highlighted “considerable uncertainty” about this assessment, because it is too early for answers to critical questions such as whether Omicron is more transmissible, leads to more severe disease, or presents a higher risk of reinfection or of evading existing vaccines.

Here’s what we do know, and what scientists are doing to work out what we don’t.

Why are scientists worried?

The Omicron variant, which was detected in southern Africa several weeks ago, caught researchers’ attention due to an unprecedented number of mutations in the “spike protein”, or the part of the virus that attaches to human cells and is typically targeted by Covid-19 vaccines and treatments.

Some of these mutations had already been flagged by researchers and Covid-19 vaccine makers for their potential to help the virus evade vaccines.

“Omicron has the kinds of mutations that vaccine makers were on the lookout for, and they have been preparing for this kind of scenario,” said immunologist Kylie Quinn, a research fellow at RMIT University in Melbourne, who called the variant’s early detection a sign that surveillance systems were working.

How these mutations work in combination “is something that we need to watch really carefully”, she said.

The variant has also grabbed medical experts’ attention due to a sharp rise in new cases in South Africa, where preliminary testing data suggested Omicron could have an advantage over the Delta variant. Delta is estimated to be more than twice as contagious as its precursors.

The jump in daily cases and early signs of an increased risk of reinfection with this variant were factors that went into a decision by a WHO advisory body to classify Omicron as the world’s fifth “variant of concern” on Friday.

Is Omicron more transmissible?

The spike in South Africa – which went from a seven-day average of around 300 new daily cases in mid-November to nearly 2,000 by the month’s end – has raised concerns. But it is not yet clear just how transmissible Omicron is or if any increases in transmissibility are related to the variant’s ability to evade immune defences, its own advantages, or a combination of the two.
“Higher transmissibility is likely,” epidemiologist Salim Abdool Karim said in an online briefing by South Africa’s health department on Monday.

“We are going to get more cases quickly, we are already seeing early evidence of this,” said Abdool Karim, adding he expected an increase in pressure on hospitals due to rapid transmission, even if the symptoms from this variant were not more severe.

Infectious diseases doctor Sanjaya Senanayake of the Australian National University said there could be confounding factors in the early South African data, such as fatigue with Covid-19 disease control measures, and a more complete picture would emerge in coming days.

“We will get more data because we’ll start to see hundreds of cases in countries around the world,” he said.

Local health investigators would then monitor how many people one case goes on to infect, what level of contact was needed for someone to spread the virus, and to what extent vaccinated people were getting infected or ill, he said.

Will existing vaccines protect against Omicron?

Major Covid-19 vaccine makers around the world are already investigating this critical question, with companies assuring the public they could update or reformulate vaccines to respond to Omicron, if needed.

Results from such laboratory investigations could take around two weeks, according to RMIT’s Quinn, as scientists build synthetic viruses or grow the real thing to see how it stimulates antibodies in blood serum taken from vaccinated people.

Real world observations about infections in vaccinated people, and comparisons between countries with different levels of vaccination, would add to what these lab studies showed, Quinn said.

Meanwhile, though it is possible existing vaccines will become less effective, as has been seen with the Delta variant, it is highly unlikely the variant would render them useless.

“Even if we see that Omicron evades the vaccine more effectively than Delta, the vaccines are still likely to have a significant impact, particularly on severe disease,” Senanayake said. “The question is by what degree will it be reduced.”

Waasila Jassat, public health specialist at South Africa’s National Institute for Communicable Diseases, told Monday’s health ministry briefing that so far the “vast majority” of new hospital admissions in the most hard-hit province were unvaccinated.

Are Omicron symptoms different?

Doctors in South Africa at the forefront of dealing with this new variant have yet to observe any signs that the variant causes more severe disease.

“But it is early, [hospital] admissions do lag by about two weeks after cases … so this is something we will watch,” Jassat said.

South African general practitioner Unben Pillay, also speaking at Monday’s briefing, said that while he had seen a “very sharp increase” in cases for about 10 days, the symptoms so far had been mild, especially among the vaccinated, and in line with other Covid-19 waves.

“We’ve seen patients present with flu-like symptoms, dry cough, fever, night sweats and general body pains and malaise,” Pillay said, adding that as a general practitioner he would see less severe cases than hospitals.

Early observations of increasing rates of hospitalisation in South Africa may be due to increasing overall numbers of people becoming infected, rather than a result of specific infection with Omicron, but more data was needed, especially on vulnerable people, the WHO said on Sunday.

ANU’s Senanayake said it would also be important to see the impact of the variant in countries with larger elderly populations than South Africa, as this group was known to be most severely affected by Covid-19.
In the meantime, it remained important to get as many people inoculated around the world with existing vaccines to add more protection against the new strain, he said.

“We can’t lose sight of the big picture, which is making sure that the world gets vaccinated.”


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