Jacinda Ardern has laid out Cabinet's plan this morning for if Covid-19 manages to slip through the border and break out in the community.
Speaking at Parliament, she said if community cases emerged, the government would impose restrictions locally or regionally in the first instance, rather than nationwide.
"Our priority will be to control any cases with the least intrusive measures, and over the smallest area we can," she said.
"We only need to look to Victoria, New South Wales, Hong Kong, Singapore and Korea to see examples of other places that like us had the virus under control at a point in time only to see it emerge again."
Rather than being a failing, Ardern said perfection in the response to a virus and pandemic is not possible.
There are now nearly 13 million cases worldwide, Ardern says when New Zealand first closed its borders on 19 March, there were only 240,000 cases.
"Experts tell us that even with the best precautions possible, the chances of the virus passing from a surface, or a contact with someone who is a carrier are high.
"We must prepare now for that eventuality and have a plan at the ready in the event that it does."
Ardern said the government will be guided by science and what they know works.
She says the government learnt a lot from the first wave of Covid-19.
"No one wants to go backwards but the reality is... it is not over."
While the alert level system remains in place, if there was to be cases of Covid-19 in the community, it would be applied on a smaller scale.
"We will move at a local or regional level ... before we would move to national."
This is about preparedness, she said, and important to also give businesses some assurances.
The alert level framework can be used locally, nationally or regionally if need be, she said.
But, the first use will be local, she said.
"In practical terms, that means doing absolutely everything possible to avoid the entire country returning to alert levels 3 or 4 as a measure of last resort."