Prime Minister Jacinda Ardern says approval for the Pfizer vaccine could come as early as Wednesday next week.

Ministers received an update on the vaccination programme today.

Speaking during the first post-Cabinet media briefing of the year, Ardern said swift progress was being made on Covid-19 immunisation.

The country could take delivery of the first batch of vaccine as soon as Pfizer could send them, she said.

As vaccines arrive, immunisation will work through priority groups.

The focus would be to vaccinate border workers and their close contacts. They will start to receive vaccinations about two to three weeks after the vaccine arrives.

A mass vaccination campaign is likely to begin in the middle of the year.

"That will be the start of New Zealand's largest-ever vaccination campaign, and that will take some time. But of course, as we've said, the most thing is when we finish, not when we start."

How many people would need to be vaccinated depended on the efficacy of the vaccine, Ardern said.

How long before New Zealand had an effective level of mass vaccination depended on several factors, including vaccine delivery and the willingness of New Zealanders to be vaccinated, she said.

While New Zealand might be ready to receive the Pfizer vaccine next week, it was up to pharmaceutical companies about when they could deliver vaccines, Ardern said.

She believed New Zealand was in a similar situation to Australia, but people were very sick and dying in other countries, and the pharmaceutical companies would be taking that into consideration, she said.

During the conference, Ardern said the Northland community case of Covid-19 was very unwelcome, but one the government had prepared for.

She asked people to scan in everywhere they went and to turn on the bluetooth function on the Covid tracer app.

Covid-19 and travel

As for Covid-19 impacting travel, Ardern said we should expect our borders to be affected for much of the year.

For travel to start we would need one of two things - the confidence that being vaccinated does not pass the virus on to others - which we do not yet know, or enough of the population needs to be vaccinated and protected, Ardern said.

Both possibilities would take some time. In the meantime, New Zealand would continue to pursue travel bubbles with the Pacific islands and Australia.

The rest of the world was too risky at this stage, Ardern said.

"Our team of five million worked too hard last year for us to risk any of the gains we have made...

"We need to remain unified. We showed last year how good we are at that and that's exactly what we intend and need to do for 2021...

"We have taken a conservative approach, and I stand by that decision. There's too much at risk. But we will keep pursuing whether or not, within our conservative approach, if it's possible."

A travel bubble with Australia was looking "increasingly difficult on a country-by-country level", Ardern said.

The way how Australian states were managing things differently offered a "level of complication", she said.

Climate change

Ardern also addressed climate change during the conference.

She said an update on climate-related transport initiatives would be announced on Thursday.

The post-Cabinet media conference is scheduled to start at 3pm.