It is critical to vaccinate the 2400-odd workers at the border who are still yet to get a single jab of the Pfizer vaccine, says Sir Brian Roche, the Government's Mr Fixit on Covid matters.
"All those people should be vaccinated," said Roche, who chairs the independent advisory group of experts tasked with providing the Government with real-time advice on how to improve its response.
"I don't know why they wouldn't be vaccinated, but it's sort of surprising. The system is there to respond to known risks in MIQ and at the border. That's why the workers need to be appropriately protected.
"Having them vaccinated is critical. We'll be pushing that really hard."
As of 9pm on June 9, there were 12,600 active border workers on the Border Worker Testing Register (BWTR), according to the Ministry of Health.
About 77 per cent of them - 9702 workers - had received two vaccine doses while 504 workers (4 per cent) had received one dose.
The remainder - about 2400 border workers - are yet to receive a single dose, though the ministry says they may have been vaccinated but this is yet to be confirmed against their National Health Index number.
"I've been assured, as I think everyone has, that [vaccinating border workers] is progressing well, but whether it's with urgency - I don't know," Roche said.
"It's clearly something we're going to have to be satisfied with. The task we've been asked to do is to think about a system that can protect us in the future."
Not all of the unvaccinated workers will be subject to the public health order, which requires all border workers in MIQ and all government workers at the border to be fully vaccinated before they can work on the frontline.
The order doesn't apply to privately-employed workers, such as the port engineer who caught the virus last year or the plane-cleaner who caught it in April.
The latest outbreak in Sydney is linked to an unvaccinated limo driver who transported international air crews.
It's unclear how many of the 2400 unvaccinated workers are privately employed and working on the border frontline.
"The big worry, of course, is the Delta variant, which is roughly twice as infectious as the original Wuhan variant," said epidemiologist Michael Baker.
He questioned whether the Government should widen the order to include all non-government border workers.
"If they're not able to be vaccinated, they need to be redeployed to jobs that don't involve any contact with potentially infectious people."
There are also 144 MIQ workers overdue for a Covid-19 test, according to the BWTR.
The Health Ministry did not provide any update on the number of non-MIQ border workers overdue for a test. On June 2, there were about 930 such workers overdue for a test.
Baker said the untested were arguably more risky that the unvaccinated, because being vaccinated wasn't 100 per cent effective.
"You really need both to get optimal protection."
The level of risk due to the unvaccinated and the untested was hard to know, he said, without seeing a breakdown of their occupations.
"But I'm very worried about what the Delta variant is clearly capable of doing. Taiwan, in particular, is a reminder of what can happen. It really succeeded for over a year and now it's gone backwards very rapidly."
The ministry said it continued to make progress on vaccinating and testing workers at the border.
National Party Covid-19 response spokesman Chris Bishop says the vaccination gap leaves the borders unnecessarily exposed to risk.
"We were told in February that border workers would be vaccinated by the end of March, yet here we are in mid-June and there's still thousands to be vaccinated.
"New Zealand deserves better."
Complacency New Zealand's biggest risk - Roche
Roche and the group he chairs, which includes three health experts and former Air NZ boss Rob Fyfe, is looking at how New Zealand can continually stamp out the virus wherever it appears when border restrictions start to loosen.
"The vaccine is part of what I describe as the ecosystem. Our primary focus is a system which includes the border, MIQ, testing and surveillance, contact tracing.
"In a post-vaccinated world where our borders will have greater freedoms, what system do we need in place to achieve the outcomes we have achieved?"
He said New Zealand's biggest strength was following public health measures and interventions that have stamped out the virus whenever it pops up.
But that had also led to complacency.
"There is a natural fatigue and complacency in normalisation of these activities, which means maybe we're not as attentive as we need to be.
"It's literally one of those situations where our greatest strength is, arguably, the trigger for perhaps our greatest weakness or risk."
Complacency can also dampen the public's willingness to follow the rules.
"There's evidence that New Zealanders' compliance with scanning and things like that isn't all it should be. There's also evidence that when there is an outbreak, the uptake is very good," Roche said.
"Every system also requires a degree of luck, but you still have to have a highly organised system. And I think we've had that - and demonstrated an ability to get effective outcomes.
"But these systems do operate on public confidence, trust and goodwill."
He said elimination was a viable long-term strategy, rather than living with the virus in communities and having it become endemic.
"If you accept there'll be relaxation of the borders over time - and it's prudent to assume that there may be incursions from time to time - then elimination is still a really important strategy and a critical strategy.
"We need a system that's going to respond where that incursion is eliminated. Look at Sydney. Look at Melbourne. When the virus appears in the community, you eliminate it."
The factors to consider for opening the border
How the borders reopen is a complex equation involving multiple factors including the efficacy of vaccines, the level of immunity with vaccination uptake, and types of variants emerging, and the number of cases in the country where travellers are arriving from.
The proportion of the population that needs to be vaccinated for herd immunity was a "$64,000 question", Roche said.
Opening the border "will be phased, it will be evidence-based, and will occur over time".
When might that happen?
"That's a decision for people well above my pay grade."
But it might be possible for unvaccinated people to be welcomed from countries where Covid-19 was eliminated, as well as vaccinated people arriving from places where it was present.
"If you have a system that has really proactive identification of the vaccination status of the person, where they've been, and what risk profile they represent, then you can have a multi-pronged approach," he said.
"There may well be returning New Zealanders who are fully vaccinated and have been to what's deemed to be a safe country. Arguably, they can walk across the border with minimal, if any, testing."
Others who are unvaccinated or arriving from a higher-risk country might have to go into MIQ, he said.
"The decision tree is complicated, and it has to be informed by evidence and sound judgment - and that's why the border is still a critical part of our prevention mechanism."
Public health measures, such as masks on public transport, will still likely play a role for three to five years, he said.
There could also be different measures for regions where vaccination rates are low.
"If this is going to be with us for a number of years, then some form of differentiation might be necessary. But I don't think it would be the starting point.
"There have been large regions of New Zealand largely untroubled by Covid. But if there's relaxation at the border, there'll be people coming in who can wander around the country, so part of the preparedness is having a national system that can be deployed regionally, or geographically, when required."
Slow set-up 'incredibly frustrating'
The group was announced in March as providing real-time advice to the Government to improve its response.
It's been over three months since then but Roche said the group was now ready to be what it was sold as.
"These things took longer than we would have liked. I find that incredibly frustrating, as do others. But [Covid-19 Response Minister Chris Hipkins] has been really clear what he wanted and we're now delivering against that."
The group has given Hipkins a review into the response to the February cluster, which saw Auckland go into level 3 lockdown.
Contact-tracing, according to the Ministry of Health, was much more efficient compared to the response to the cluster in August last year.
Only 59.4 per cent of contacts for the August cluster were isolated within 48 hours of the case being notified. The gold standard is 80 per cent, and for the February outbreak it was 84.4 per cent.
Roche said the system had responded well but there were still lessons to be learned, including how introducing the terms "casual-plus" and "close-plus" had muddied the waters.
"Sometimes complications, whilst being technically correct, are confusing to the general public.
"Ultimately, those are things that ministry is working through."