Ardern said that although Omicron could be a milder illness for some people, the Government was expecting many more cases and that would put pressure on the health system.
She said there had been a range of modelling and the Government had made plans for a wide range of situations from high numbers of cases to low cases.
Ardern said the different models have a "vast variation" and she has asked experts to try to compare them and come up with a more consistent analysis.
This was partly because of the new nature of Omicron, with WHO only declaring it a variant of concern eight weeks ago.
But no matter the modelling, she said that every booster shot in a Kiwi arm will help reduce the impact of Omicron on the community.
When asked if she could guarantee the New Zealand intensive care system could cope with Omicron, Ardern said that looking overseas every country's health system had been put under pressure by the variant.
Overseas health research organisation the Institute for Health Metrics and Evaluation (IMHE) earlier said New Zealand could be facing 50,000 daily Omicron infections by Waitangi weekend, peaking at about 80,000 each day a few weeks later.
The IHME projections also predicted an outbreak in New Zealand could last about three months, with death rates projected to total more than 400 by May 1. Daily fatalities are predicted to spike at about 10 through mid-March.
But the best thing Kiwis could do was get their booster shot, regardless of the modelling, she said.
She said the Government recommended people get booster shots four months after having their second Covid vaccination shot.
That was based on advice from health experts and clinicians.
She also rejected claims the Government had requisitioned rapid antigen tests (RATS) from those ordered by private businesses.
She said RATS have a large variation in accuracy rates - some as low as 30 per cent.
It was important the Government ensured that quality RATS were brought in.
When asked when ordinary Kiwis would be able to buy RATS from their local pharmacy so they can test for Covid, Ardern said the Government was focused on ensuring every Kiwi could be tested.
The Government's three-phase Omicron plan would initially focus on providing traditional PCR tests and then moving to RATS as more are available.
PM on 30-year inflation high
On inflation hitting a 30-year high today , Ardern said commentators had predicted rising inflation rates and that it was largely the result of global inflation pressures.
"New Zealand is alongside every other country that is experiencing high crude oil prices," she said.
She rejected criticism that Government spending had contributed to inflation, saying the Government's wage subsidy pack during the Covid lockdowns had been critical to keep the economy ticking along.
Ardern is in Wellington today and has been promoting the vaccines and boosters rollout at a vaccination centre.
In relation to booster shots for Māori, Ardern said the gap between booster shots and second vaccination shots was a decision for medical experts, not one for the Government to make in isolation.
Ardern said that a key plan to ensuring Māori are looked after during the Omicron outbreak is to make sure that people are being cared for when they go into isolation either with the virus or as close contacts.
She said she had been working with Māori health providers and community groups to ensure people would be cared for properly when isolating.
An Omicron case was confirmed in Queenstown and a person in Gisborne tested positive for Covid.
This week the Government set out further details of how it will contend with Omicron, and director general of health Dr Ashley Bloomfield is due to talk to Māori health organisations today after concerns that they were not consulted ahead of the plan being formed.
They are also likely to talk about the rollout of boosters to Māori after issues with the rollout of the initial vaccination doses.
It also comes after news the Ministry of Health instructed rapid antigen test companies to reserve any incoming orders of the tests for the government response, rather than delivering them to the private companies that had ordered them.
Yesterday, Associate Health Minister Ayesha Verrall unveiled the three-phase plan to combat Omicron.
Despite still relatively low Omicron case numbers - the outbreak rose by 15 cases to 56 yesterday - based on overseas evidence, 10 cases could reach 1000 cases in six to 12 days, she said.
On Tuesday, Ardern said the rapid antigen tests would be an increasingly important part of the government response once Omicron case numbers grew beyond 1000 a day – and would be used in critical businesses to try to reduce the disruption to those workforces by staff being off sick or isolating.
Ardern also pointed to the problems in the supply of the rapid antigen tests, noting 83 million rapid antigen tests were on order but only about 19 million of those were either in the country or due to arrive over the next five weeks. The delivery schedule for a further 40 million was pending.
Ardern did not say then that the Ministry of Health was now taking the tests that had been ordered by private companies, but did say the Government would continue to "pull out all the stops" to secure what was needed.
