Moving Auckland out of level 4 lockdown won't require having zero 'mystery' Covid-19 cases, Prime Minister Jacinda Ardern says.

Cabinet has made an in principle decision that Tamaki Makaurau will move to alert level 3 next week and will review the settings on Monday.

Ardern told Morning Report good surveillance testing rates especially from seven key Auckland suburbs would give further reassurance.

University of Auckland epidemiologist professor Rod Jackson says one more week of level 4 restrictions is "probably not" a long enough time to contain the Auckland Delta outbreak.

Jackson told Checkpoint it was possible the outbreak could be contained in a week if people followed the rules - but he was "a bit pessimistic". "We can knock it on the head if people follow the rules, but… people aren't following the rules," he said.

Ardern said advice from the public health team, the Ministry of Health and the Director-General of Health was that a week was long enough and provided that extra ability to do surveillance testing.

"The proposal and the view is that we would be able to move at that point."

Moving down a level would not necessarily depend on having no so-called mystery or unlinked cases, she said, because they were worried about only a few of them.

A "handful" of the 17 still-unlinked cases were of concern, with genome sequencing on others indicating a relatively short chain of transmission.

"So that means that there's a handful we are honing in on. If we are able to get good testing around the areas where we they've been and those suburbs that does helps give us extra reassurance.

"If we're then not seeing further ones cropping up in those areas, that gives us further reassurance.

"And then it's just the specifics of what's happening with the cases that do come through."

People in seven key Auckland suburbs are being encouraged to get a Covid-19 test even if they have no symptoms. Mt Eden, Massey, Mangere, Favona, Otara, Papatoetoe and Manurewa are under increased scrutiny because of unlinked cases, or clusters that may have unexpected cases.

Ardern said level 3 had been used previously to manage outbreaks from the beginning, and was not suddenly removing restrictions.

Vaccinations

No decisions had been made on requiring people to be vaccinated to attend certain gatherings as had been done in other countries, Ardern said.

"But what I am mindful of is going forward our events sector and those who are involved in large events will be looking for us to design ways that their events are future-proofed.

"That's the call on us, that's the work we need to do. We want to find a way that when you're planning a large scale event that you can feel confident that it will go ahead regardless.

"So we'll keep doing that thinking."

The prime minister said the government would continue to emphasise people going to drive-through or walk-in clinics as the easiest way to get vaccinations done, though mobile vaccination units were being built into services.

The clinical leader of the city's vaccination programme, Dr Anthony Jordan, said they were in the final stages of organising mobile vaccination units to go street to street, offering Covid-19 vaccinations in areas where there may be low coverage or where people may be struggling to get to a clinic.

"We have them in some specific areas where we have got target populations, they have been used as a tool before," Ardern said.

"But at the moment what we're trying to continue to drive people towards are things those drive through clinics, those walk in clinics, places where we can do a large number very easily.

"Our vaccine team are working on some of those mobile options as well. It has been a small scale part of our rollout to date.

Community health providers were also offering pick-up services and other solutions to meet the needs of their communities.

"It is already happening in some areas, it's just how large scale it will be in the future."