Cabinet ministers will meet this afternoon to assess the traffic light settings across the country, most crucially, whether Northland will drop to orange.

The outcome will be announced on Thursday as Labour MPs gather in New Plymouth for a new year caucus get-together.

The Cabinet meeting - the first this year - is set down for 4pm today and will canvass an array of matters relating to Covid-19.

As well as the regional restrictions, ministers are likely to also discuss the traffic light system's broader parameters, the planned border reopening, and testing requirements.

Northland is the only region to remain under red restrictions with the remainder of the country at Orange.

Just 86 per cent of those aged 12 and over in Te Tai Tokerau have received two doses of the Covid-19 vaccine, compared to the national average of 93 per cent.

Prime Minister Jacinda Ardern this week encouraged New Zealanders to get boosted, warning that an eventual Omicron outbreak was "a case of when, not if".

Regions would shift to the toughest red light setting if the new variant was found to be spreading through the community, she said.

"What I expect is, over the coming weeks, to be able to share with you some of the additional preparation that has been done, over and above the work that we did on Delta, for the specific issue of Omicron," Ardern says.

"We have the ability to learn from other nations and see ... the way that Omicron is behaving and prepare ourselves."

Ardern signalled there will be changes to the processes and requirements surrounding testing, isolation and contact tracing.

Director-General of Health Ashley Bloomfield yesterday told Morning Report officials are developing advice on whether the traffic light system needed to be strengthened in the face of Omicron.

"It's quite clear that Omicron does escape vaccination," Bloomfield says.

A group of public health experts this week warned that the traffic light regime would not be sufficient to contain the spread of Omicron.

University of Otago epidemiologist Michael Baker recommends an urgent tightening at the border and a delay of its phased reopening.

-RNZ/Craig McCulloch.