Prime Minister Jacinda Ardern says the Omicron outbreak is likely to peak in three to six weeks.

She said at that point the country would move down the traffic light settings, easing off gathering limits.

"We are predicting cases will continue to double every three to four days ... it's likely then that very soon we will all know people who have Covid, or we will potentially get it ourselves," Ardern said.

She said there were three reasons that was no longer as scary a prospect as it used to be.

"Firstly, we are highly vaccinated and that happened before Omicron set in."

Secondly, that meant Omicron would be a mild to moderate illness and boosters make hospitalisation 10 times less likely.

The third factor was that public health measures like masks, gathering limits and vaccine passes were helping slow down the spread to ensure everyone who needs a hospital bed could get it.

"So far, that plan is working.

"We have 46 cases per 100,000 people, compared to 367 in New South Wales and 664 in Victoria at the same point in the outbreak.

"Our hospitalisations, too, are well below Australian states at a similar time."

Ardern said cases were likely to peak in mid- to late March, some three to six weeks away.

At that point a rapid decline, followed by cases stabilising at a lower level is likely.

Ardern said at that point, the traffic light system could change, because it meant public health measures used to protect the health system could be eased off.

She said vaccine passes have been necessary as the "least bad option", but they have always been temporary.

After we come through a wave and a peak of Omicron, many unvaccinated people will have been exposed to Covid-19.

She said coming through the peak would allow the Government to ease mandates in places where they were less likely to impact on vulnerable people.

"They will remain important in some areas though, for some time."

Mandates are likely to remain for some areas - particularly sections of the healthcare workforce - but there will be a narrowing of where they were required.

She said it was hard to set a date, but the Government needs to ensure we are "well beyond the peak" and that the pressure on the health system was manageable.

The reasons not to do away with the traffic light system entirely was so the country was prepared for new variants and potential future waves, and the coming of winter at the same time as flu returns, she said.

"To summarise then, the coming weeks . . . Covid will increase, and rapidly.

"There will be disruption and pressure from Omicron.

"We must brace through the next six weeks, but we can do so knowing the future with fewer restrictions is near because that has always been the course we have chartered."

She said as we reach the peak and start to come down we could all move towards a new normal we can all live with.