This week's rogue case of Covid-19 has prompted a flurry of questions about New Zealand's exposure to the coronavirus. Science reporter Jamie Morton looks at three of them.
With a pandemic running rampant around the world, the risk at New Zealand's borders is growing greater by the day.
Yet, even after 100,000 returnees coming home since March last year, and with strict entry requirements largely making only permanent residents and citizens eligible to come here, the country's managed isolation and quarantine (MIQ) facilities are still running close to capacity.
Otago University epidemiologist Dr Amanda Kvalsvig pointed out MIQ guests are arriving from countries that have very high infection rates, with increasing numbers of more spreadable variants.
"Guests and staff in MIQ now have a high risk of becoming infected and that also creates risk for the whole country, as we've just seen with the current Northland case," she said.
"It's not in people's best interests to travel all this way, only to become ill on arrival in New Zealand and perhaps infect others too."
She said a temporary reduction in MIQ numbers was among those steps that could give our system a chance to adjust to this new risk.
"For example, slightly lower occupancy would make it easier to work on ventilation in MIQ hotel rooms and bring them up to a safer standard."
There have also been calls to drastically tighten travel restrictions for people coming from mass-infected countries - something the Government showed little indication of doing today.
Prime Minister Jacinda Ardern said no country had barred their citizens from returning, as this would essentially leave them stateless.
She added the Government had already moved to require pre-departure testing before flying here, along with new arrivals staying in their MIQ rooms before their first test results came in.
"We are constantly looking at what we can do to create further restrictions and protocols to protect people, both in our facilities but also in our wider population," she said.
"But you would be hard pressed to find anyone with more stringent measures than we have at our border."
The possibility that the virus could have been passed from one isolating returnee in Auckland's Pullman Hotel to another through ventilation systems is a curious one.
As Health Minister Chris Hipkins said this afternoon, it was also the least likely, with surface contamination or close contact the more probable explanations.
Still, do air ducts in managed isolation and quarantine (MIQ) facilities pose an overlooked Covid-19 threat?
The fact that so many people have now passed through MIQ facilities, with proportionally few catching the virus within them, might suggest that risk is low.
Otago University infectious diseases expert Professor David Murdoch explained the virus was passed on through droplets - and the smaller aerosols could be suspended in the air and possibly pass through ventilation systems.
"There are lots of questions from researchers around this at the moment."
There's been some research to suggest the same ventilation systems found in many modern office buildings, which are designed to keep temperatures comfortable and increase energy efficiency, may increase the risk of exposure.
That was "mixing" ventilation - where vents are placed to keep the air in a space well mixed so that temperature and contaminant concentrations are kept uniform throughout the space.
One study has suggested another mode, called displacement ventilation, could reduce the risk of mixing and cross-contamination of breath.
Safer ventilation has been repeatedly singled out by public health experts as one issue the Government could look more closely at to improve its MIQ systems.
Still, like Hipkins, Murdoch said this potential risk needed to be put in the context of the myriad other ways the virus could spread - like through lift buttons and rubbish bins, as seen in New Zealand already.
The Government today announced that border and MIQ staff, and their close contacts, would be vaccinated within weeks - and the rest of the country could expect a wider roll-out midway through the year.
Medsafe will be seeking advice and recommendations from the Medicines Assessment Advisory Committee (MAAC) next Tuesday about the Pfizer and BioNTech vaccine.
Would that vaccine, and the other Janssen, Novavax, and University of Oxford-AstraZeneca vaccines New Zealand has pre-purchased, work just as well against the emerging UK, South African and Brazil variants?
"There are thousands of variants now out there, but with most of them there is no difference to the way that your immunity recognises them," University of Auckland vaccinologist Associate Professor Helen Petousis-Harris explained.
"But if the shape of the target that you've made an immune response against changes significantly, that could make it less effective."
Pfizer-BioNTech said its vaccine was still effective against the UK and South Africa variants - although it was slightly less protective against the latter.
"Unlike for influenza vaccines, the reduction in neutraliaation that might indicate the need for a strain change has not been established for Covid-19 vaccines," said a study that tested the Pfizer-BioNTech vaccine on the variants.
AstraZeneca was currently testing its vaccine against them.
Petousis-Harris said it was critical to consider the difference between vaccine efficacy - or how it performed under ideal and controlled circumstances - and "effectiveness", or its performance in real-world conditions.
"Effectiveness can be ultimately much higher than efficacy, because of its additional effects on transmission," she said.
"So you could have a very average vaccine that could potentially get rid of a disease, just because of the more indirect effects that you see once you start using it."
The bigger issue could be around the level of uptake among Kiwis, given the vaccine won't be mandatory.
Asked about vaccine "sceptics", Ardern said that would be a smaller group in New Zealand - while a larger concern was vaccine hesitancy, or those on the fence.
She said this is something that can be overcome.
"They need as much information as possible."
She said there was going to be a vaccine education push before the roll-out, to make sure people are educated about it.
She said the "team of 5 million" expects the Government to "do its homework" when it comes to the vaccine - and that homework will be shared with Kiwis, she said.
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