Prime Minister Jacinda Ardern says no one wants to go backwards but the reality is ... it is not over.

On a Facebook livestream, Ardern has outlined scenarios where the country will need to go into different levels of lockdown in different regions if COVID-19 was to spread into the community.

"We will be guided by science and what we know works."

She says the government learnt a lot from the first wave of COVID-19.

"No one wants to go backwards but the reality is... it is not over."

"We will move at a local or regional level ... before we would move to national."

This is about preparedness, she said, and important to also give businesses some assurances.

The alert level framework can be used locally, nationally or regionally if need be, she says.

But, the first use will be local, she says.

Ardern says borders would need to be established to contain locally or regionally, and would be supported by agencies.

A regional level 4 would be to contain an outbreak.

"We would maintain a certain level of flexibility depending on what sort of outbreak we have."

She noted that in other countries, apartment blocks, workplaces and suburbs have all been locked down.

"The message here is in that eventuality, we wouldn't necessarily be moving all of New Zealand at once..."

New Zealand has learned that things move quickly and giving more than 24-48 hour frameworks would lose effectiveness, she says.

Health Minister Chris Hipkins says rapid contract tracing is vitally important.

"The more accurate that is early on, the more targeted we can be in our approach."

Ardern says she doesn't put a timeline on how long New Zealand's borders will be closed, "but it continues to be an area of risk that needs to be managed."

She says the news of Judith Collins becoming the new opposition leader is taking a "bare minimum of her thinking".

"I think right now, politicking doesn't matter much to them (the public)."

Hipkins says the contact tracing system will be at a gold standard when every New Zealander is keeping a good record of where they have been and every business has QR codes.

"It's reliant on all of us."

He says over recent weeks, he hasn't been as diligent as he should have been but he's stepped up his game.

"What if tomorrow there is notice of a case and we need to notify anyone who came in contact in or near that place," Ardern says.

She says people who test positive for COVID-19 may be removed from the community, and their homes, and put into a facility.

Hipkins says they are looking at different options for further contract tracing.

Ardern says there is an element of personal responsibility in all of this.

But the NZ Covid Tracer app is not a complete solution, she says.

"The Covid tracing app is all about people controlling their own data," Hipkins says.

In regards to a bubble with Rarotonga, Ardern says she's continuing her discussion with the Cook Island's prime minister.

Very strong physical barriers would be needed at airports for this to happen because there is currently no way to separate someone who is positive from someone who has come from a place with no cases, Ardern says.

She says any trans-Tasman bubble would be restricted to what is happening in each country.

"Obviously, now is not the time."

Ardern says on the issues of masks, there would be very specific guidance if there were to be outbreaks.

The NZ Covid Tracer app provides speed, unlike other apps, she says.

"I can tell people hand on heart that it is an app that looks after your personal security."

-RNZ