There are 49 new Covid-19 cases today, all of which are in Auckland. This is the lowest number of cases in six days.

Director-General of Health Dr Ashley Bloomfield said it was reassuring case numbers had continued to drop, with four fewer cases announced today than yesterday.

The reproduction rate remained under 1, and "we are successfully breaking chains of transmission". It is the lowest daily number of cases in six days, Bloomfield said. 

Of the cases reported yesterday, only 23% are considered to have been infectious in the community.

Of the cases linked to the outbreak 33 people are in hospital, of which eight are in ICU, including two who are being ventilated.

Prime Minister Jacinda Ardern said one of the people in hospital was an 18-year-old,  which showed people should not assume catching the virus would not affect them.

Bloomfield said it was "sobering" that six cases in Auckland were under the age of one. He reminded people that it was safe to receive hospital-level care under alert level protocols.

There were 16,755 tests processed nationwide yesterday.

The seven-day rolling average for tests is 31,600.

PM on South Island moving to level 2

Ardern would not be drawn on the chances of the South Island moving to alert level 2 next week, but said if it was safe the Government would make the change.

"We will review in a week's time. We are really keeping our options open there. We will undertake a very genuine risk assessment about the ability to move levels."

The amount of time the South Island would stay in alert level 3 had not been predetermined.

"Yes, we haven't had a case in the South Island for a long time - and we want to keep it that way.

"Our goal is to get everyone back to the fewest restrictions possible as safely as possible."

Bloomfield said Ministry of Health teams were reviewing alert level 2 settings, which could include increased mask use.

PM's golden rules for alert level 3

Regions outside of Northland and Auckland move to alert level 3 at midnight tonight.

Ardern reminded people to continue to be cautious as much of the country moved to level 3.

"We have a second day where our numbers have declined we  want that trend to continue but we do have some hard work in front of us still.

"We want the tail of this outbreak to be as short as possible, but that is up to all of us.

"So to everyone, please do stick with it and as we transition to level 3 please do remain absolutely cautious."

She said under level 3 some people who are isolated and who need child care support can bring another person into their bubble under alert level 3.

Contactless delivery can occur but all staff are legally required to wear a mask for outwardly facing businesses such as supermarkets and petrol stations.

The "golden rules" for everyone south of Auckland: Keep your distance from people, continue working from home if possible and keep children at home with you. They should only go to school if parents are essential workers.

Public venues remain closed such as gyms, pools, playgrounds and markets.

Travel is restricted for work for those needing to pick up goods in a contactless way.

From tomorrow anyone aged 12 or older can book a vaccine.

Funerals, weddings and Tangihanga are allowed for up to 10 people.

Businesses must be contactless and meet requirements such as wearing face coverings to operate.

Prison officer tests positive

A Corrections officer at Springhill prison has tested positive for the virus. There are 23 staff who had contact with that person. They are isolating and getting tested. There are 123 inmates in the unit where the staffer worked, they have been segregated and all will be tested.

The Corrections officer was fully vaccinated.

They were asymptomatic.

How did Delta get into community?

Ardern says she "lies awake at night" trying to work out how the Delta strain got into the community. The outbreak is linked to a returnee at the Crowne Plaza managed isolation facility. How it got from that facility into the wider public remains a mystery.

The Government is still unsure how the variant travelled from the Crowne Plaza into the community. Many scenarios have turned out to be "dead ends", Bloomfield said.

"Now we're left with theories that don't have people to people contact, but simply the air," Ardern said.

The Crowne Plaza continues to be empty. Ventilation specialists are doing another assessment of the building to see if anything can be improved.

On boundary rules said personal travel between alert levels is highly limited, Ardern said.

Today's drop in case numbers come after Monday had a substantial drop in case numbers with 53 reported compared to more than 80 each of the preceding days.

Auckland will remain in level 4 for two more weeks, while the rest of the country south of Auckland will move to Level 3 at midnight today.

All going well with testing, Ardern said yesterday Northland would move to level 3 at 11.59pm Thursday.

This morning Covid Response Minister Chris Hipkins told Newstalk ZB it was still too early to say whether yesterday's lower case numbers was a trend, but he would be keeping his fingers crossed.

He wanted to see the numbers drop and stay low but it was still too early to say if that would happen.

 Ardern is also expected to reveal more information and clarify mixed messages about vaccine stocks.