One more week of level 4 restrictions is "probably not" a long enough time to contain the Auckland COVID-19 Delta outbreak, University of Auckland epidemiologist Professor Rod Jackson says.

Prof Jackson told Checkpoint the Government's decision on Monday was the right one, "but I think they should have said: 'Unless Aucklanders are staunch, it's going to be at least two weeks'."

The Auckland region will remain in level 4 lockdown until 11:59pm on Tuesday, September 21. The government said it is aiming, in principle, to move Auckland to alert level 3 from then.

The rest of the country will also stay in level 2 restrictions.

Prime Minister Jacinda Ardern is urging Aucklanders to remain in their bubbles. Professor Jackson said he thinks people breaching those rules is what is causing the ongoing numbers of new cases.

"Delta's a new disease, really. [We] probably shouldn't call it COVID anymore. It's so much more infectious than the previous variants," he said.

"We can knock it on the head if people follow the rules, but… people aren't following the rules."

Prof Jackson said it is possible the outbreak could be contained in a week if people follow the rules, "but I'm a bit pessimistic.

"The good news today is that all bar one [of the new COVID-19 cases] can be linked, so we know where they came from.

"That's really good news, but it's the few others out there that we just don't know about. And the thing about Delta is, left to its own devices - and those mystery cases are in fact left to their own devices - one person, on average, infects six other people. And they infect six other people.

"So it's … 1200 and something in the same time that the previous variants got to 16.

"This is completely different from last year… We've got a whole new disease to deal with."

Professor Jackson said rapid antigen testing could help, but the main issue is potential complacency under lockdown.

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"If you're going to leave the home… behave like you've got COVID-19, and everyone you come in contact with has COVID-19.

"Because the way we stop this and we can stop it in its tracks is keeping infected people away from uninfected people.

"It's as simple as that. We could knock it on the head in two weeks, even a week, if people followed those rules.

"For Aucklanders today, if you've got anything, a tickle in your throat, if you feel unwell, go and get a test. But stick to your bubble. That's how we stop this."

Prof Jackson told Checkpoint he believes Auckland can get rid of this outbreak. But only two things can be done for Delta. "That's lockdown and vaccination."

Getting vaccinated is key to preventing any future lockdowns like this, he said.

He believed 95 percent of the eligible population aged 12 and over need to be vaccinated before lockdowns can be dismissed.

Currently only around 1.4 million people in New Zealand have received both doses of the Pfizer COVID-19 vaccine.

"We can get there, it's not a big deal.

"We don't have horribly low rates given when we started. We started late, but we had to start late because we had a much higher bar of safety.

"Once we knew the vaccines were safe - and these are the world's best vaccines, they're much safer than anything else - now we have to ramp up as fast as possible.

"I think we need 24/7 centres. We need to take the vaccine to the people, so I think we need mobile units. We need to be going around the suburbs and we need to be taking the vaccine to the people."

Deputy Prime Minister Grant Robertson dismissed the idea of mobile vaccination units, saying they could have more potential for vaccination problems or vaccine stock maintenance issues.

Professor Jackson said the government is aware the country needs up to 90 percent vaccination coverage already.

"The Danes, 60 years and over, they're already up to 95 [percent].

"One hundred percent of All Blacks are vaccinated, and 97 percent of Cook Islands adults are vaccinated. We can get there.

"But how did they do it? They went to the people. And I think that message will get through to the politicians soon enough.

"I can see that lots of pop up centres can be a problem, but what's wrong with mobile centres? You can set them up professionally. You can make sure they've got the right refrigeration, everything.

"But I think the only way we're going to get up to 95 is to take it to the people. It's not that people are anti-vaxxers. That's a very small minority. It's just that for a lot of people, they still don't get it.

"They've never experienced COVID-19 themselves, obviously. I mean how many people in New Zealand have had it?

"Very few, very few New Zealanders know anyone who's had COVID-19.

"Even fewer know anyone who's died from COVID-19, so to the average New Zealander, it is still not a big deal. So we have to take [vaccinations] to them."