Omicron: What we know so far12/26/2021
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Does Omicron really lead to milder disease? How crucial is a booster shot? How long will this wave last?
Answers to these questions can vary, sometimes by the hour as scientists and public health experts race to study the virulence and severity of the new Omicron strain.
Omicron negative stain images created at the Doherty Institute. Credit:Dr Jason A. Roberts, Doherty Institute
Due to the rapid spread of the virus, studies are released and widely reported without being peer-reviewed. Sample sizes can be small. Experts warn the speed and shape of Omicron outbreaks in South Africa and the UK may look vastly different in Australia.
But some concrete findings are beginning to emerge in global studies, even as we enter a fluid and highly unpredictable chapter of this COVID-19 pandemic. Here is a snapshot of what the latest research says about Omicron.
Does Omicron really make you less sick?
A growing body of evidence from South Africa, Denmark and the UK suggests the risk of admission to hospital with Omicron is between 15-80 per cent lower compared with Delta.
The latest report by London’s Imperial College, last Wednesday, found those infected with Omicron were 40-45 per cent less likely to be admitted to hospital for a night or more, compared with the Delta variant.
Data from Denmark suggests those testing positive to Omicron were three times less likely to be hospitalised, while a major analysis by the UK Health Security Agency finds they are 50-70 per cent less likely to need hospital care.
A study by South Africa’s National Institute For Communicable Diseases, finds suspected Omicron cases were 80 per cent less likely to go to hospital, but the analysis does not account for vaccination status.
While this is fairly reassuring, Monash University epidemiologist James Trauer said there were no guarantees Australia’s outbreak would look the same.
Australia is unique in its relatively high vaccination rates and lower natural infections, meaning our background immunity levels are different to South Africa and the UK.
“It’s not yet clear how key natural infections will be to the outcomes in these countries,” Dr Trauer said.
In the UK, over half the English population had already possibly been infected with COVID-19 when the new variant hit.
In South Africa, only about a quarter were vaccinated and the country had high natural immunity.
But with South African data now broken down by age in findings backed up by studies in the UK, it was now much clearer that severity for every age group was less for Omicron when compared with other variants, Dr Trauer said.
“I think we’re beginning to see that direct comparison able to be made between Delta and Omicron, particularly in places that have really good data like the UK,” Dr Trauer said.
But why would illness caused by Omicron be less severe?
Researchers at Cambridge and Hong Kong universities have found in non-peer-reviewed studies that the variant replicates much faster in the bronchus 24 hours after infection — which is why it transmits so fast — but is far slower when spreading in the actual human lung tissue, possibly indicating lower disease severity.
There is mounting evidence that Omicron causes milder disease, but experts caution against overstating this, with the sheer number of infections set to overwhelm already overstretched healthcare systems.
By spreading faster than any other variant, Omicron may ultimately cause more severe disease and death. It will be weeks before these impacts come to bear in Australia.
Do masks help?
The effectiveness of masks in protection against Omicron is not yet known. Early suggestions are that the virus can pose a higher risk than Delta and it might therefore be safer to wear higher filtration masks.
Lidia Morawska, researcher and director of the WHO-collaborating International Laboratory for Air Quality and Health said: “The better fitting the mask, the more protection.
“There haven’t been enough studies on this, but if Omicron settles in the deeper part of the respiratory tract, this is where the particles are the smallest.
“Smaller particles follow the airflow, which means if there are gaps between the mask and the face, of course the mask will provide less protection.”
How much more protection will a booster shot give me?
Antibodies in vaccinated people are far less effective at neutralising Omicron than with Delta, work from Columbia University and overseas data shows.
However, many studies also show that vaccines still fend off severe disease, and booster shots serve as a crucial defence.
Hours after the federal government announced it would fast-track the booster shot program, co-chair of the Australian Technical Advisory Group, Allen Cheng, told The Age and The Sydney Morning Herald that “having two doses and a booster gets you to the same place with Omicron as two doses did with previous variants”.
But will three doses be enough?
Israel wants to administer a fourth dose to people over 60, amid signs that immunity from a booster shot starts to wane more rapidly than with Delta. The UK’s Health Security Agency finds protection against the strain is 15-25 per cent lower from 10 weeks after the third dose.
The issue of boosters remains vexed.
The World Health Organisation’s Director-General Tedros Adhanom Ghebreyesus has continued to warn that countries cannot boost their way out of the pandemic, with poorer countries not yet meeting minimum vaccination targets. “The vast majority of hospitalisations and deaths are in unvaccinated people, not unboosted people,” he said.
Omicron: A shorter wave?
South Africa has seen a significant drop in COVID-19 cases in recent days, from more than 26,000 on December 15 to 19,000 on December 24. Some experts suggest this could be a sign that the country has already reached its peak.
University of Melbourne infectious diseases epidemiologist and vaccinologist, Fiona Russell, who has been tracking Omicron hospitalisations globally said: “I think, based on the data that we’re seeing from other countries, certainly from South Africa, this thing explodes over six to eight weeks, and then that seems to decline again.”
Dr Trauer said a spike in cases would inevitably subside as immunity improves, but whether Australia’s trajectory would follow South Africa’s remains to be seen.
“When you see a dip in cases after a huge spike like that, it means enough people have been exposed and infected that you generate enough population immunity for things to start coming back down again,” Dr Trauer said.
“We can’t keep going up forever, so we will at some point turn around, but we can’t assume we will have the same pattern of epidemic as these other places.”
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