Ardern said Omicron cases are growing but this is not unexpected, and vaccinations are helping slow the spread of the virus.
"Two weeks into our Omicron outbreak we have a three-day rolling average of around 200 cases, lower than many of the predictions."
She said we are now seeing a similar level of cases as the peak of the Delta outbreak but hospitalisation rates are much lower.
With about 51 percent of those eligible now boosted, she encouraged more uptake, saying: "it was two shots for Delta, and three for Omicron".
Today was the start of the "big boost week" she said, with more than 150 sites open in Auckland.
From today, the extra million people who became eligible on Friday would begin receiving text message or email alerts.
"Boosters are the most important determinant of how we will weather the Omicron storm."
Ardern said as announced today, $400,000 would be allocated to the rural support agencies and those supporting Maori agribusiness to help prepare for Covid in the rural setting.
In response to a question, she said the funding for rural support was getting ahead of the problem, rather than dealing with current spread.
Asked if lockdowns were still on the table, Ardern said with the tools the government has, it lessened the need for them. She said the government had also made a deliberate decision to begin reopening from the end of February because that would give time for more than 90 percent of eligible New Zealanders to have access to a booster.
Asked about modelling released by Te Punaha Matatini today, she said much of what the government was using was scenario planning rather than "accurate forecasting", and uptake of the booster would be the main determining factor in slowing the outbreak.
"It's not out of our hands. We do have some control over what happens next," the prime minister said in regard to different modelling scenarios.
She said the country needed to prepare for low and high-case scenarios, and with Delta the government had stress-tested DHBs last year ahead of summer, which would help inform the country's preparedness for Omicron.
On waning immunity, research suggested a shorter window in decreasing the likelihood of passing the virus on, but the vaccine's ability to prevent severe disease lasted much longer, she said.
Covid-19 Response Minister Chris Hipkins said the best preparedness for the health system was doing everything possible to prevent severe disease in the first place.
He said boosters were important along with things like mask use and adaption based on emerging international evidence.
Ardern said Omicron had tested hospital systems throughout the world.
Hipkins said people working in intensive care units were worried and anticipated coming under increased pressure, but the advice from health professionals was they were ready.
"They deal with peaks in ICU demand, they have to sometimes make decisions about how they best meet that increase ... they are as well prepared as they are able to be but as I think the prime minister and I have both just said, the best way to prevent a huge influx into the health system is to avoid as much as we can having a huge influx of people having to go to hospital."
Asked about her plans to travel overseas later this year, Ardern said she did not have any more specifics on her plans for trade delegations, including whether she would be going to China.
Earlier, Ardern told Morning Report she believes New Zealand's Omicron peak may be in late March.
This morning, hundreds of protesters against Covid-19 vaccine mandates gathered on Parliament grounds and vehicles from the protest convoy blocked a nearby street.