The traffic light system puts all our eggs in the vaccination basket, but Omicron will require a more diverse set of tools than previous variants, Marc Daalder reports
Analysis: Omicron spreads like lightning.
Within weeks of arriving in the United Kingdom, it was already infecting 200,000 people a day, according to modelling from the British government's health experts.
In London, on December 1, just 1.6 percent of cases were suspected to be Omicron. A week later, it was 34.9 percent. A week after that, it was 84 percent.
You barely need genomic sequencing to detect an Omicron outbreak – once the daily case curve goes vertical, the culprit is clear.
Everywhere it spreads, Omicron has been characterised by a doubling time of two days. In other words, you might have 10 new cases on Sunday, then 20 new ones on Tuesday. By the time the next Sunday rolls around, you'll have more than 100 cases a day.
In New South Wales, where Omicron has exploded as a result of super-spreader events, daily Covid-19 case numbers are hitting new records every day. Tuesday's total of 3057 cases is nearly double the pre-Omicron record – and officials there expect to see 25,000 daily cases by the end of January.
That's in a place experiencing summer and where the population has recently received two doses of mRNA vaccine, just like New Zealand.
The news of a new, more transmissible variant will feel like deja vu for New Zealanders who have seen the Alpha, Beta and Delta variants arise within the past year. But it's hard to overstate how different Omicron is from everything that's come before, or how this new variant makes fighting Covid-19 a whole new ballgame.
The Government has shortened the gap between second doses and boosters in an attempt to boost our immunity against Omicron. Covid-19 Response Minister Chris Hipkins has also promised that regions with Omicron cases will move straight to the red setting of the traffic light system.
But the traffic light system was designed for Delta, which could be corralled and slowed with high vaccination rates. Health experts aren't so sure that it will work against Omicron and are already calling for the return of some aspects of the alert level system. That the Government is mostly forging on ahead with the policies it developed for Delta means we could risk following the same path as New South Wales.
The case for optimism
It isn't all doom and gloom. There are important tools we have going into the fight with Omicron that we lacked in our battles with previous variants.
Vaccination is the obvious one.
While two doses of the Pfizer vaccine are less effective in preventing people from being infected with Omicron (more on that later), most vaccinated people are still well protected from severe disease or death.
Essentially, vaccines stimulate and train two different parts of our immune system: antibodies and T-cells. Antibodies help recognise and combat the virus when it first arrives in the body. Strong antibody responses meant that virus particles which entered the body of a vaccinated person usually didn't have a chance to take hold and spread.
Antibodies are trained to respond to a particular antigen - in the case of the coronavirus vaccines, we've been training our antibodies to recognise and fight the spike protein. The problem is that Omicron's spike protein has so many mutations it isn't always recognised by antibodies. That's part of the reason our protection against infection from vaccines wanes against Omicron.
The good news is that we also have T-cells - killer white blood cells that seek out infected cells and destroy them. These care less about the specifics of the virus and more about identifying and destroying anything that doesn't belong in the body. While antibodies are the vanguard, T-cells are the infantry who will fight to stop the virus from seriously harming us. Vaccines (or prior infection) train them too, meaning that vaccinated people are still protected against severe disease or death even if infected with the Omicron variant.
Another bit of good news is that booster shots seem to supplement our antibodies, bringing protection against infection back up above 70 or 75 percent.
There's a lot of discussion about whether Omicron causes disease that is inherently less virulent (severe) than previous variants. It's hard to say what's inherent and what's a result of the populations the virus is infecting. In South Africa, most of the cases have been young people who are less likely to end up in hospital anyway, so that will bring the hospitalisation and death rates down.
In Europe, where the virus is now spreading, vaccination rates are high. While many more vaccinated people are vulnerable to being infected by Omicron, only a few of these are more vulnerable to being hospitalised by it.
Either way, compared with the Delta wave over winter, South Africa's Omicron wave has seen similar case numbers but only a fraction of the hospitalisations and deaths.
The case for caution
New Zealand, of course, is different from South Africa.
Put aside the population factors, the differing immunity profiles (we're more highly vaccinated but have less immunity from infection) and differences in government and health systems.
Our handful of brushes with Covid-19 outbreaks have been negligible compared to what South Africa or most of the rest of the world have gone through. Even a quarter of the deaths of South Africa's Delta wave would be by several orders of magnitude the most deadly wave of the pandemic for New Zealand. It would be nine deaths a day, or more than 3000 deaths if sustained over a year.
There's also no reason to believe that the virus wouldn't spread more widely in New Zealand than in South Africa.
The tide is now turning there, with case numbers dropping.
It's hard to say exactly what caused this turnaround. Certainly, not everyone who could be infected has been. Trevor Bedford, an American virus modeller, says he expects Omicron to infect about half of the susceptible population in the United States.
The Ministry of Health's chief science advisor Dr Ian Town told Newsroom on Tuesday that he expected we'd see a different pattern than that experienced in South Africa.
"I think the situation in South Africa is really quite different to what we're seeing in Europe - particularly the UK at the moment - and in Australia. There, of course, the number of people who have experienced Covid is very high so they have natural immunity as well and the vaccination will have topped that up," he said.
"So I think that dynamic is very much in a previously-infected population. Yes, the initial wave seems to be flattening but I think more worrying for us is what's happening in Europe, in Australia and in places people come to New Zealand from because that'll be the risk that presents at our borders."
Te Pūnaha Matatini disease modeller Michael Plank agreed that we shouldn't necessarily take South Africa as a model.
"These different mixes of immunity, we don't really know yet how that's going to pan out," he said.
"Australia is obviously the closest comparison, particularly with them being in the same time of year, the same season as we are."
The Government's response plan
University of Auckland microbiologist Siouxsie Wiles also points to Australia - and New South Wales specifically - as a place to watch. That's less as a model for how Omicron will spread in New Zealand and more a warning as to how it could spread if we don't get our response right.
"At the moment, Sydney is going to show us what happens with Omicron when you've got a [highly] double vaccinated population and very little restrictions," she told Newsroom.
"Their contact tracing is already broken. When people test positive, they're now having to contact their own contacts."
This isn't the first time we've looked to Australia for a reminder of the importance of responding forcefully to new outbreaks. Victoria's 111 days of lockdown in 2020 reinforced the move to Level 3 in Auckland's August 2020 outbreak and Sydney's massive Delta outbreak underpinned the justification for this year's national Level 4 lockdown and extended Auckland restrictions.
Wiles' worry is that we won't actually take the lesson on board this time. She isn't alone in thinking that the red light setting won't be enough to slow the spread of Omicron.
"We now don't have the shield that is the rapid move up the alert levels. What we've got is 'red,'" she said.
"We do have limits on gathering sizes, but they're not enough. And we do have masks mandated, but probably not in enough places. So it partly might do something. But it is so much more infectious that what you're giving with one hand, the virus is taking away with the other. It does feel a bit like we're back to square one again."
"The traffic light system was really designed for Delta and for a population with high vaccination rates that were effective for the Delta variant," Plank agreed.
University of Otago epidemiologist Michael Baker said it was little more than an "indoor vaccine mandate". That was all well and good when a vaccinated person was 80 to 90 percent less likely to be infected with Covid-19 than an unvaccinated person and much less likely to spread it if they were infected, but Omicron changes the calculus.
Real world data from spread of the variant in South Africa indicates two doses of Pfizer provide just 33 percent protection against infection.
The problem with the traffic light system is that it represents a departure from the "swiss cheese" model of risk management. No one tool is a silver bullet against the virus, but if you layer measures on top of one another, they can significantly dampen spread.
The traffic light system puts all of our eggs on one basket: Vaccination. Against Delta, the vaccination slice of cheese had few holes and anything that got through those would likely be stopped by masks or mopped up by contact tracing.
Against Omicron, there are more holes in the cheese slice and they're much bigger. Masks as our only backup won't do the trick.
"We were largely turning our back on public health and social measures and relying on vaccines. I think Omicron is really showing us that we can't do that at this point in time. I do think we need to revive the alert level system in case we need it," Baker said.
"The worst case scenario is that we get Omicron circulating very vigorously over the winter along with a bad flu season and it does threaten the health system and we go back to using the alert level system and even a partial lockdown."
Boosters not enough
Instead, the Government is trying to shore up the vaccination barrier through boosters. Boosters can raise effectiveness against infection to 70 or 75 percent. But only 6 percent of double vaccinated New Zealanders have had a third shot.
Compare that to more than 40 percent of the United Kingdom's full population having had a booster, and Omicron still spreading like wildfire there.
"What we know is that stopping transmission, preventing deaths, preventing all of the long-term health consequences is going to be best for us in the long-term and in the short-term frankly. We just need to do the things that work," Wiles said.
"One of the things that we know works is stopping people from having contact with each other and if they do have contact with each other, wearing masks. We've got to totally up our mask game and just think about the quality of the masks that we're wearing."
It seems unlikely that the Government will step in here, like it has in the past. Instead, we're now going to find ourselves in the same situation as those in other countries: Having to make our own personal judgments about what is unsafe and what is worth the risk.
Where the Government may not mandate mask-wearing, health experts might still advise we do so. Where the Government doesn't cap gatherings or require us to reduce social contact, the Covid-19 situation may compel us to do so of our own accord.
The outlook for the next few months is grim. Plank believes Omicron will almost certainly end up in the community.
"I don't think we're going to be in a situation where we're trying to keep Omicron out for 18 months like we were with Delta or the variants that came before it," Plank said.
Hipkins seems to regard the six-week extension of the reopening plan as little more than a delaying tactic to get more New Zealanders boosted.
Once it arrives, Omicron will rapidly become the dominant strain circulating in the community. It may not totally outcompete Delta - if people infected with one variant don't get immunity from the other, the two could coexist and fuel simultaneous or alternating surges in cases and hospitalisations.
We don't know what the long-term prognosis is for Omicron. The rapid retreat of cases in South Africa could indicate it operates in spikier waves than previous variants. But a spike is the precise thing we want to avoid if we want to keep the health system standing.
"The speed it can spread at is quite incredible and so just the sheer number of cases in a short period of time means that even if the hospitalisation is much lower than Delta, it could still put more pressure on healthcare," Plank said.
In March 2020, we talked about flattening the curve and spreading the same cumulative caseload over a longer period of time. That meant healthcare capacity would never be exceeded in a given day, or week, or month.
Omicron makes that significantly more difficult because it infects so many people so much more rapidly. Wiles says we now must prepare ourselves to do what it takes to squash the curve, even if that means digging measures out of the alert level toolbox rather than relying solely on the traffic light system.
"It feels very much like we're back at square one."
