Vaxx Populi: Omicron has a higher effective reproduction number than Delta, so can vaccines protect against more hospitalizations and deaths? Time will tell.
It’s been 11 days since the World Health Organization declared the newest mutation of the SARS-CoV-2 virus to be a variant of concern and named it Omicron. Since then, researchers have been hard at work figuring out its characteristics and what sort of threat it poses to the world.
Their work is still in the preliminary stages and will both change and evolve in the days and weeks ahead. There are at least 25 studies of Omicron planned in Britain alone that aim to learn more about its household transmission risk, population symptomatic reinfection risk, and predictors for being an Omicron case.
Yet already clues are emerging that suggest Omicron could be “trouble with a capital T”.
Here’s the latest Vaxx Populi FAQ on Omicron:
How was Omicron discovered and why are researchers worried?
All those general questions and answers are found in the first Vaxx Populi FAQ from Nov. 29. Here’s the link.
I keep hearing reports that Omicron may be milder than Delta. Is that true?
We don’t know.
Right now, many of those getting Omicron in South Africa are young people, and that age cohort is expected to have milder symptoms than those, say, 70 and older. So it’s unclear if reports of milder symptoms are because of who is getting it now or whether it really is milder for all age groups.
On Saturday, Dec. 4, the South African Medical Research Council (SAMRC) published data from the epicentre of its outbreak, the Tshwane District of Gauteng Province, about early features of those admitted to hospital with Omicron. Cases are rising exponentially, from fewer than 1,000 on Nov. 29 to more than 3,000 on Dec. 3. And between Nov. 14 to 29, some 166 people were admitted to hospital with COVID-19, representing 25 per cent of all public and private hospital admission.
While emphasizing the data only captures the very beginning of the outbreak, SAMRC revealed two main findings: that the majority of COVID patients aren’t dependent on oxygen, like in previous waves, and most discovered they had COVID only after being admitted to hospital for other health reasons.
“A snapshot of 42 patients in the ward on 2 December, 2021 reveals that 29 (70%) are not oxygen dependent. These patients are saturating well on room air and do not present with any respiratory symptoms,” the SAMRC report stated. Furthermore, there was only one person in ICU and four needed critical care.
What all experts caution is that there is no way to extrapolate what could happen based on that very preliminary data from one district in South Africa, which has a vaccination rate less than half that of Canada. It could mean that those who are vaccinated have decent protection against Omicron, or there could be other factors at play.
Is Omicron spreading quickly?
As of Dec. 5, there are 905 confirmed cases of Omicron and nearly 50,000 suspected cases around the world, according to a tracker from Newsnodes.com. A week before, there were 184 confirmed and 1,305 probable cases.
Trevor Bedford, a scientist who studies the evolution of viruses at Fred Hutch in Seattle, detailed the origins and path of Omicron in a long Twitter thread: “Omicron appears to have emerged around Oct. 1 and has taken eight weeks of exponential growth to ‘suddenly’ have sizable impacts on case counts and hospitalizations in Gauteng. This ‘suddenly’ is the nature of exponential growth.”
The variant has spread around the world, sparking local outbreaks. “As a broad analogy, if it took [roughly] 8 weeks for Omicron to grow from initial spark into local epidemic in South Africa, I would expect very roughly 8 weeks from today for secondary epidemics to begin to manifest,” he stated.
Now, more and more, public health authorities are reporting such secondary outbreaks. In Norway, more than a dozen people who contracted COVID-19 at a Christmas party on Nov. 26 have the Omicron variant even though they were all fully vaccinated and tested before the event. Cases have been mild to date, with no hospitalizations, CNN reports. Meanwhile after a party of 150 high school students in Denmark, at least 50 are now Omicron positive.
In Britain, “one in 200 people testing positive in London last week are likely to have had Omicron,” explained Theo Sanderson, the Sir Henry Wellcome Fellow at the Francis Crick Institute in London, after combing through the latest technical briefing on variants from the UK Health Security Agency (formerly Public Health England), released on Dec. 3.
On Dec. 2, Toronto Public Health declared an outbreak at the Toronto East Detention Centre after testing revealed that a correctional officer who had contracted COVID had Omicron and four inmates had subsequently tested positive, though the strain of their viruses hadn’t been determined.
If Omicron does turn out to be milder than Delta but much more transmissible, is that better or worse than what we’re experiencing with Delta?
It will likely be worse.
Early modelling using South African data indicates that Omicron is significantly outpacing Delta, with an effective reproduction value (Rt) of more than three. To put that in context, Canada’s current Rt is 1.1, as of Dec. 3, according to the Centre for Mathematical Modelling of Infectious Diseases in Britain. And Delta is the dominant variant here.
So if Omicron’s reproduction rate is much higher than that of Delta, then the math means more hospitalizations and more deaths. In a widely distributed graphic and social media thread from December 2020, Adam Kucharski of the London School of Hygiene and Tropical Medicine in Britain shows the relationship between transmissibility and death.
The key message, Kucharski explained, is that “an increase in something that grows exponentially (i.e. transmission) can have far more effect than the same proportional increase in something that just scales an outcome (i.e. severity)”.
What about the effectiveness of our vaccines?
Experts believe that they still offer protection against Omicron but the question is how much protection and how well it will do in preventing hospitalizations and deaths.
That SAMRC report from Gauteng Province showed that of 38 adults in hospital with COVID, 24 patients were unvaccinated, six were vaccinated while the status of the remaining eight was unknown.
What about the protection of natural immunity from already having COVID-19?
In South Africa, it’s estimated that around 80 per cent of the population has had COVID-19, yet already there are early indications that such natural immunity may not be enough when it comes to fighting off Omicron.
On Dec. 2, a preprint study by South African researchers was posted on medRxiv that compared incidents of reinfection after the introduction of Beta, Delta and now Omicron in the nation. Their conclusion at this very early stage of research: “Population-level evidence suggests that the Omicron variant is associated with substantial ability to evade immunity from prior infection. In contrast, there is no population-wide epidemiological evidence of immune escape associated with the Beta or Delta variants.”
What can I do here in Canada?
Get vaccinated, whether it’s your first, second or third shot, and do it as soon as you are eligible.
On Dec. 3, the National Advisory Committee on Immunization (NACI) “strongly recommended” third shots of an mRNA COVID vaccine within six months of a second shot for:
- People in long-term care homes and other congregate settings
- People 50 and older
- Adults in Indigenous communities
- Frontline health–care workers
- Those who got only viral vector vaccines (AstraZeneca or Johnson & Johnson/Janssen) for their first two does.
For adults 18 to 49, NACI just “recommends” that they get a third shot within six months of their second dose, but puts in a caveat that those doses are with “consideration of jurisdictional and individual risks.”
Provinces are already divided between which NACI path to follow: Alberta has opened third shot eligibility to all adults 18 and over. On Dec. 13, all Ontarians 50 and older can start booking third shot appointments.
As with first and second shots, it will take time for the third shots to be fully effective, so getting as many people vaccinated as soon as possible is crucial to building one barrier against Omicron.
Article From: Maclean’s
Author: Patricia Treble
