Ardern said the first stage is the one the country is in now, after an Omicron cluster was found in the community without an identified link back to the border.
Stage one is for a thousand cases or less, which the Prime Minister said could take two weeks to unfold.
Initially, the goal is to stamp out clusters and use testing and tracing, to slow the Covid-19 variant down while vaccination programmes continue.
There are the same settings as now for Covid cases and contacts, and the use of the most accurate PCR tests. Cases still have to self-isolate for 14 days and contacts for 10 days. Anyone with symptoms would be tested at a testing station in the community or main health provider. Rapid antigen tests will be rolled out to providers.
Ardern called stage two a "transition", when cases will be higher and the focus will be more on people most at risk of severe illness. There will be more use of rapid tests.
During stage three, Omicron case numbers would be in the thousands. There would be major changes to contract tracing, the definition of close contacts and isolation requirements. Overseas, the definition has been eased and isolation times shortened.
Talk from the very top about thousands of Omicron cases coming our way would have been unsettling for Kiwis emerging from the summer haze and into yesterday's wet and gloomy weather in Auckland.
The new stages reflect how the Covid-19 variant behaves. Delta is a middle-distance runner and Omicron is a sprinter, jumping out at pace. It has an incubation period of about three days, which makes it hard to detect before it spreads.
It is shaping as a two to three-month wave, going by trends overseas where cases are falling in some countries after incredibly high case peaks and much disruption to health systems, businesses, services and supply chains. It has reached the stage in countries such as the United States and Australia where sick essential workers are being asked to work.
The Government has quickly come under pressure for what it is yet to commit to.
Health experts want booster eligibility, currently set at four months after the second vaccine shot, reduced further. Even when people get the third shot, there's still the usual time lag of two weeks before immunity levels rise.
The Government is considering changes to its mask advice, which has been inadequate compared to overseas countries for a long time.
If advice includes "any face covering will do" as an option, people who don't like the idea of masks, don't know any better, or can't afford or don't want to shell out money for good quality ones, will jump at it. But some types of masks offer little protection at all.
As of Sunday, the Government hadn't considered subsidising N95 masks to make them free to everyone or sending rapid tests to every household for free.
The relaxing summer is effectively over. We are back in the coronavirus storm.
