Omicron having swept the globe, fortress New Zealand is now bracing for its own wave of the mass-spreading variant. How are we placed to face it and what more can we do? Science reporter Jamie Morton looks at five key areas.
When New Zealand was first confronted with the coronavirus threat, two years ago this month, the natural step was to dust off our pandemic playbook.
Within this national emergency manual was a particular strategy designed for quashing a runaway surge of influenza cases, of which we came to hear much: flattening the curve.
A few weeks later, of course, it was ditched in favour of all-out elimination.
So, it's with acknowledged irony that an architect of our zero-Covid plan, Otago University epidemiologist Professor Michael Baker, says reverting to curve-flattening should now serve us best against the faster-spreading menace that is Omicron.
The super-dominant variant's much shorter incubation period and doubling time – each estimated at a mere three days - meant we could no longer dream of crushing outbreaks like we did in 2020, and may well have done again with Delta.
Baker said Omicron's remarkable spreading power effectively removed one of our trustiest tools – contact tracing.
Yet, unlike in early 2020, we were now equipped with vaccination, a suite of health measures and well-tested systems, a pandemic-ready public, and a library of lessons gained directly from overseas experience.
Just as we pivoted from elimination to "tight suppression" to tackle Delta, Baker said New Zealand now had to turn to "mitigation" - something that could reduce disruption, help shield the most vulnerable, and keep our hospitals from being disastrously swamped.
It meant doing all we could – especially now - to squash a curve perhaps built of hundreds of thousands of Omicron infections.
"Public health now has to be at the core of everything," Baker said.
"My colleagues have looked at what's happened overseas – even in rich countries with excellent healthcare - and found there's just no way our frontline system alone can cope with such a wave of infections."
Modelling reports here have warned of dramatic surges: up to 65,000 people in the Wellington region alone could contract Omicron over three months.
Although just a fraction of such volumes were expected to need hospital care, the numbers were high enough to still heap heavy pressure on an already-strained health system.
Late last year, a leaked report revealed there were a little more than 100 intensive care unit (ICU) beds available across district health boards.
While the Government has since insisted that capacity could be surged to up to 550 ICU beds, clinicians have suggested a more realistic figure might be closer to 350.
Health experts say a crucial part of easing the squeeze on hospitals will be adequately managing infected people within their own homes.
That's just what the Government's new Care in the Community model – where patients are phoned by health providers within a day of testing positive, and provided a care pack within 48 hours – was set up to help with.
But as flaws have already been found in the regime, such as instances of Covid-positive people leaving isolation early, there have been appeals from the sector to shore it up before it's tested with thousands of cases.
At this point, the Government's three-phase plan involved pointing contact tracers to people most at risk, and to critical workers.
In the third phase, when cases numbered tens of thousands, the definition of contact moved largely to people sharing a case's household, while clinical care would be targeted at those with high needs.
Professor Tony Blakely, a New Zealand epidemiologist based at the University of Melbourne, has seen first-hand what Kiwis might be in for over coming months.
But Australia's Omicron ordeal had yielded some useful insights, which he said New Zealand needed to take on board.
A big one was doing everything possible to protect the elderly and those with co-morbidities.
"That means their hunkering down, and families dropping the shopping off while the infection runs on through."
Keeping Omicron out of aged-care facilities was much harder, he said, but rest homes could minimise the risk by ensuring staff were boosted and wearing high-grade masks - and even isolating residents in their rooms if needed.
"We've now had around 600 deaths in aged-care here within the last two months, which shows you where a lot of the mortality is concentrated."
The risk within schools could be reduced through measures already being put in place, he said, such as masking, ventilation and vaccinations.
"This isn't just about protecting kids against getting severe infections, which few of them will, but dampening down transmission."
Regardless, he warned that up to half the population may become infected with the variant.
While there were fears reopening borders might worsen the wave, it was expected the Government's just-announced phased approach wouldn't result in a sudden surge of infected travellers on top of a national outbreak.
Covid-19 modeller Professor Michael Plank said that, by the time the first set of restrictions lifted late this month, case numbers would anyway be in the thousands - and the vast majority of vaccinated adults would be eligible for their booster.
After a chorus of calls from health experts, the Government this week confirmed it would follow several Australian states and cut the eligibility interval for the Pfizer booster from four months to three.
It couldn't have come much later.
As at this week, just a third of the eligible population over 12 had received the third dose.
Although many of those were people who needed the shot most – our elderly, vulnerable and critical workers – that still left some 2.5 million Kiwis sitting on two doses only, just as Omicron began to take flight.
New UK data has highlighted why it's so important to boost. If someone received their second Pfizer shot around six months ago, their protection against catching the virus and suffering symptoms may have dropped to just 10 per cent.
The booster could rebuild that immunity by up to 75 per cent, two to four weeks after being administered.
Although its effectiveness against symptomatic disease gradually waned too – as far as 25 to 40 per cent over four months – experts hoped the booster rollout would time in well enough that most Kiwis would bear good immunity as Omicron hit hardest.
Cutting the interval quickly made the shot available to another million Kiwis – and if they got their dose right now, there'd be enough time to build antibodies in time for a potential March peak.
Perhaps most importantly, the booster was estimated at 90 per cent effective at keeping people out of hospital - offering a substantial tool to flatten the curve.
Plank saw high booster uptake as crucial.
"It can easily reduce the number of people being hospitalised by a factor of 50 per cent – if not more."
University of Auckland senior lecturer Dr David Welch wanted to see the Government churning through at least 80,000 booster shots every day, which it had the capacity to do.
"This will greatly increase the immunity we have in the population and reduce the impacts of the Omicron outbreak."
Director-general of health Dr Ashley Bloomfield told reporters this week the Government ultimately hoped to see booster uptake of between 95 and 100 per cent of the population.
Asked why the Government hadn't cut the interval time weeks ago, when other countries already had, Bloomfield insisted "we were early movers".
"And what's different between us and those other countries that do have a three-month interval is we're doing it very early on in an outbreak, whereas they were doing it in response to a really large number of cases in the community."
Baker felt New Zealand's goals with masks should be similar to vaccinating, given their importance in blocking transmission.
"As with vaccines, you want high coverage and you want effectiveness, but at the moment, neither of those requirements are being met," he said.
"A lot of people are now saying fabric masks have no role anymore. I think they may have some role – but they need to be high quality, and we have no standard on fabric masks."
He said New Zealand was slow to adopt mass-masking – something long part of Asian cultures – and remain concerned we still weren't making the most of the simple-yet-effective measure.
Those same worries likely precipitated the Government's recent move to crack down on people covering their mouths with bandanas or pulled-up shirts.
From now, people visiting places like restaurants, cafes and bars would also need to mask up whenever they got up and left their tables.
Yet that didn't change the fact that many of these indoor settings - where people could still sit, talk and eat unmasked – remained high-risk environments for super-spreading events.
Elsewhere, experts have pointed to masking among children.
Although the tighten-up now means kids on publicly funded school trips must wear masks – as teachers and pupils at year 4 and above must do in classrooms under the current red regime – Baker and colleagues have suggested pre-school children could also be fitted with them where possible.
That was on top of existing mask requirements in shops, clinics, aged-care facilities, councils, courts and public venues, as well as on flights, buses, ferries and taxis.
What else could we do?
Baker's Otago colleagues have long been pushing for a national mask strategy that would give the public better guidance and equitable access to high-grade masks like N95 or P2 respirators.
Otago University epidemiologist Associate Professor Amanda Kvalsvig wanted to see the Government do more to promote these, which could offer more than 90 per cent protection against most particles when fitted properly.
"Respirator masks are standard wear in many countries and there is abundant clear and straightforward advice about their use," she said last month.
"Even without instruction, N95-type masks tend to fit better around the face than surgical masks, which typically bunch up at the sides so they have gaps for the virus to enter."
Once Omicron overruns our contact tracing capability, rapid antigen tests are likely to prove another line of defence.
There's currently only around one for each Kiwi in the country but, within eight weeks, the Government expected to have more than 50 million of these quick-fire tests in the community.
Through to June, a total 126 million have been ordered – and they'll likely be needed.
Over the peak of the outbreak, modelling has indicated New Zealand may need to churn through a staggering nine million each week.
"Although RATs are not as sensitive as PCR tests, they have the big advantage that they can return a result in minutes rather than days," explained Dr Dion O'Neale, a modeller with Te Pūnaha Matatini.
"This is important, because it means that it is possible to potentially confirm infections much sooner after exposure, and for people to respond accordingly by self-isolating in order to break any further chains of transmission."
It meant people could quickly learn whether they were safe to return to work – something that would help keep essential services operating at times when the country was awash with Omicron.
While RATs were more likely than standard PCR tests to return more false negatives, they were also most likely to give positives for people carrying higher viral loads.
"This is a pretty good approximation of the time when people are also more infectious, hence it gives us a chance for people to avoid infecting others during that period," O'Neale said.
"False positives from RATs only become an issue when they are being used in a population with very low prevalence, that is, when we would otherwise expect almost all test results to come back negative."
As more Kiwis sought tests, he said the number of false positives from RATS would thus become "negligible", relative to the number of true positives.
"Other countries with Omicron outbreaks have seen test positivity rates of 10 to 20 per cent," he said.
"At these levels, a positive result from a RAT test is highly unlikely to be a false positive."
Along with people using RATs to test themselves if suffering Covid-19 symptoms, Baker said they'd be important for self-screening before visiting a vulnerable or aged relative.
"That's because we know that so many Omicron cases are asymptomatic, and it's good to see many essential workplaces are already providing for their employees," he said.
"When PCR testing gets so saturated that people simply can't go to their local testing station, it might be good for people to have a stack of these at home – potentially in every household."
Above all else, Baker was worried New Zealand's long-entrenched health inequity would again see vulnerable groups such as Māori bear the brunt of the wave.
Māori accounted for half of all cases in the Delta outbreak, despite representing just 16 per cent of the population.
One modelling study that drew on case data from 2020, and controlled for age and pre-existing conditions, showed Māori were two and a half times more likely to need hospital care than non-Māori - while the risk for Pacific people was even greater, at three times higher.
"We're likely to see these patterns play out again in the Omicron wave, unless we plug the equity gap," Plank said.
"That we're shortening the gap to three months is really good news on this front, because many Māori who were vaccinated relatively late in the rollout are now going to be eligible straight away, or much sooner than they would have been."
Māori health researcher Dr Rawiri Taonui said Māori vaccination rates were still well behind national rates – or 85 per cent double-jabbed, compared with 94 per cent nationally.
In remote rural areas – sometimes an hour's drive or more from the nearest medical centre – rates were even lower.
The disparity was echoed in pediatric vaccination rates, with 21 per cent of Māori aged 5-11 having received their first dose, versus 39 per cent nationally.
In terms of cases, Taonui was pleased to have seen Māori rates drop dramatically over summer, which he put down to health workers' efforts over the Christmas break.
"Māori have only accounted for 10 per cent of cases over the past six days – but I think there'll be a new vector by which Omicron will move into Māori communities, and that's schools reopening and kids mixing."
That imminent risk could be reduced by local vaccination efforts targeting low-decile schools, he said, and the Government reducing the eight-week interval between child doses to three weeks.
"I'd say we only have between 10 and 14 days to kick-start these and a number of other things."
Another obvious need was more support for Māori whānau to manage Omicron at home.
"When Covid first arrived, we had a big emphasis on food parcels during lockdown; this time, we need food parcels but also basic medicines like ibuprofen, paracetamol and cough syrups, and other items like masks and disinfectant," he said.
"I saw someone on social media say they'd put a care kit together for around $65. We've got a lot of families that can't even look at that kind of money.
"Instead of food parcels, we basically need Omicron crates."
This week, Prime Minister Jacinda Ardern told media the Government was working with Māori providers around care in the community, having already stood up a system that she said worked with Delta.
"Now we need to make sure that it's able to expand, to be able to deal with what will be a larger number of cases, but actually where the majority won't need the kind of level of care that Delta may have required."
When the Government released its three-phase plan last month, however, health experts were quick to point out there was little detail about how it would address health inequity.
"There are still some Māori who are not engaged with primary healthcare, for a variety of reasons, yet the plan is community management," said Dr Rachel Mackie, chair of the Royal NZ College of General Practitioners specialist Māori representative group, Te Akoranga a Māui.
"More information on how that would practically happen is needed. The lack of planning for our Māori population is disappointing, and needs to change."
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