By Rowan Quinn of RNZ
Alert level 3 is being called a roll of the dice that could either eliminate Delta or send the country back into level 4.
From tomorrow, Auckland will make the move after five weeks at alert level 4.
Covid-19 modeller, and Aucklander, professor Shaun Hendy said the greater freedoms allowed at level 3 were a risk.
"Part of me is ... thinking about takeaways but I am also concerned about what we will see over the next couple of weeks. I think now we have moved to level 3, the next two weeks are crucial," Hendy said.
Modelling the latest situation had been tricky because of the small number of cases left and the unknown quantity of how Delta behaved in New Zealand, he said.
In one scenario contact tracers could beat the outbreak in a couple of weeks
But in another, case numbers could steadily rise - like in Victoria and New South Wales - and Auckland would have to go back to alert level 4.
That could then lead to an outbreak which dragged on for weeks - or months, Hendy said.
Te Ropu Whakakaupapa Uruta, the National Māori Pandemic Group, called for alert level 4 to stay in place.
Co-leader Sue Crengle said they were disappointed in yesterday's decision.
They worried a big outbreak was brewing - and also looked to New South Wales where cases had been low for weeks then started to go up and down, she said.
"And then they lost control and we're really fearful that in six or seven weeks we may see that," she said.
Professor Crengle hoped her group would be proven wrong but worried the stakes were too high - especially for more vulnerable, and less vaccinated, Māori populations.
Most experts agreed the move to alert level 3 was a risk.
Its success was partly dependent on how well Aucklanders stuck to the rules.
Epidemiologist Rod Jackson said most had done a great job so far and any rule breakers at alert level 3 were probably the same people who would break them at level 4.
He backed the move to alert level 3.
That was because the source of most infections was known and there has been little transition outside of homes, he said
Alert level 3 was still very restrictive but struck a balance by allowing more businesses to open and a few more freedoms.
"It's good for our psyche and good for the economy but still designed to stamp out Covid," he said.
Prime Minister Jacinda Ardern said Aucklanders had done the hard work at alert level 4 when there was uncertainty about the outbreak but now health authorities had a much greater understanding of the situation.
The virus could again be eliminated under alert level 3, she said.
Motorists are being warned to expect hazardous driving conditions.