Covid-19 Response Minister Chris Hipkins says there are four new cases of the virus in managed isolation as he reveals the latest on New Zealand's vaccine rollout.

Hipkins said the vaccine delivery schedule for August was confirmed for 1.5 million doses.

Hipkins said it was important now there were many ways people could get vaccinated.

This included mass vaccination events - the first being in Manukau for three days from the end of July.

The mass vaccination would be targeted at Manukau Institute of Technology students and their families - and would be an opportunity for people in group 4 to be vaccinated ahead of schedule.

Hipkins said they were looking at vaccinating 15,000 people - 5000 a day - at the event and the plan was to do this event earlier, but it was constrained by supply.

People would need to book in for the mass vaccination event, and would be encouraged to gather friends and family to join them. They could then book their second vaccination for six weeks later on the day.

South Auckland was an area of focus for mass vaccination events, Hipkins said, because of the population and exposure to the border. Other population centres with density could expect to see similar events to "top up" vaccination rates.

Overall DHBs were tracking about 6 per cent ahead of schedule on vaccinations, Hipkins said.

There had been 1,404,343 vaccination doses delivered, including 564,789 who had received their second dose and were thus fully vaccinated.

On people arriving and returning from Australia without doing pre-departure testing, Hipkins said it was a combination of people accidentally forgetting and some deliberately avoiding it. Some had been sent back on flights to Australia, while returning New Zealanders who needed to do managed isolation had been charged for it.

The Ministry of Health was issuing 16 $300 infringement notices to border workers who had not complied with testing orders, Hipkins said.

He expected there would be more of them to come, Hipkins said.

Hipkins said he did not expect them to be employed by the Government, so likely not MIQ workers

Hipkins announced that all border workers who need to be regularly tested will, from mid-August, be able to have saliva PCR tests instead of the more invasive nasopharyngeal testing.

Such testing will be rolled out for those who need to be tested every week, and progressively rolled out for the other workers over several months.

The Ministry of Health has been reluctant to allow saliva testing to replace the nasopharyngeal PCR test, even though that has been recommended by the independent advisory group chaired by Sir Brian Roche.

Roche had previously said in September last year - as part of the testing review he did with Heather Simpson - that saliva testing should be rolled out as quickly as possible.

Hipkins said it was hoped this change would boost testing levels among MIQ staff.

Hipkins said advice a week ago from the Ministry had informed the decision to allow saliva testing to replace nasal swabs.

The feedback, with saliva testing at a limited number of sites, was that if they had to do nasal as well there was no real benefit.

It was hoped now there would be much more "enthusiasm" and saliva testing would be rolled out to more sites, Hipkins said.

The advice continued to be for diagnostic purposes that if someone had symptoms nasal testing was the surest option, he said.

Hipkins said the Ministry had been "cautious" in its advice previously. He acknowledged they needed to move faster in responding and adapting, while investigating robustly, as new technologies became available.

Covid-infected mariners

Yesterday, 13 more crew members tested positive for Covid-19 in managed isolation after coming off a ship docked at Wellington - and another ship has docked at Port Taranaki with crew suffering "flu-like" symptoms.

The 15 crew members from the Spanish-flagged Viking Bay deep sea vessel, which included the two people who tested positive last week, are all in a quarantine facility in Wellington.

Everyone the mariners from the Viking Bay vessel interacted with had been fully vaccinated and were fully protected, Hipkins said.

New Zealand's role with helping re-crew vessels was to help them arrive into the country and transfer to vessels as smoothly as possible. That had been done in this case, Hipkins said.

It was his understanding they had the Delta variant, Hipkins said.

One of the five Covid-negative crew members has become symptomatic and has been moved to the Grand Mercure MIQ facility.

Joint Head of Managed Isolation Megan Main said the mariners at the Grand Mercure were completely separated from other guests.

The infected crew members were at sea and needed assistance and New Zealand had an obligation to provide them assistance, Hipkins said.

Those who had arrived by plane to replace the crew members had all had pre-departure testing.

Testing continues for the vessel, where reports of flu-like illnesses originated last week. It had applied for a change of crew while berthed at Port Taranaki.

Ballot system considered for MIQ

Main said in regards to bots assisting with bookings for MIQ slots, the tech could help but a person still needed to do the actual booking.

This was not a system problem so much as a demand versus supply problem, Main said.

The aim was to make it as equitable as possible. A US-style green card lottery ballot system has been considered, as well as introducing a waiting list, she said.

Main said the Government needed to be careful they kept the system stable.

In April and May rooms were available to September, where supply exceeded demand, while now they had moved back the other way.

One of the challenges with a wait list was it pushed the problem further up the pipeline. They did not want people staying on the wait list when they did not need their booking anymore.

Demand was currently very high, Main said.

In terms of aligning flights with MIQ slots, as with the NSW situation, Main said they had set up a whole new situation to manage returns. They could do this for a short period of time, but it was quite complicated and involved hourly conversations with airlines. This was sustainable for a short burst but was not a long-term situation.

Hipkins said regardless of what system the Government introduced to allocate MIQ spots to returning New Zealanders demand will continue to outstrip supply.

"There is a reason I stood here several months ago and said to New Zealanders who need to come home 'now is good' - it's because we had space and because we knew that there was a likelihood at some time in the future demand would once again build to outstrip supply.

"New Zealanders abroad wanting to come home were forewarned of that potential quite some time ago."

Today the Herald revealed Prime Minister Jacinda Ardern has spoken with Pfizer boss Dr Albert Bourla twice this year, including once last week after the delivery of a crucial shipment of Pfizer doses.

The Government has faced criticism over its vaccine rollout, and Hipkins has conceded expectations could have been better managed - especially for group 3, including those 65 and over.

The Government announced its first purchase agreement with Pfizer in October last year - for 1.5 million doses - subject to the vaccine successfully completing all clinical trials and receiving Medsafe approval.

Medsafe approved Pfizer on February 3, and the vaccine rollout started later that month. As of last Wednesday, just over 500,000 people - about 10 per cent of the population - were fully vaccinated.

Amid criticism for allowing international mariners infected with Covid-19 onshore putting the country at risk, Ardern said New Zealand "has an obligation" to help those in distress.

She was, however, asking more questions about obligations to help with re-crewing efforts for similar foreign-flagged vessels that had no economic interest and were "against our environmental interests".

Auckland University professor Des Gorman told Newstalk ZB he was "very concerned" and said they should never have been allowed onshore in the first place.

The whole point of the quarantine system was to leave the virus offshore, with measures like pre-departure testing, he said.

"Here we have shifted the risk from offshore to onshore. Now we have 15 highly infectious people sitting in a building in Wellington. This is not how you do business."

He said it was "very likely" they had the highly infectious Delta variant and said they should be confined to their hotel rooms to prevent any outbreak.

Ardern said the crew aboard the Viking Bay fishing ship should not have been kept at sea.

New Zealand had an obligation to those who "may be in distress or need medical assistance" within the country's geographical boundaries, she said.

The mariners are at the Grand Mercure in Wellington, which has opened up a second floor to isolate them. The 5-star hotel is a dual-use managed isolation facility which houses both infected and non-infected returnees.

Ardern said the Government had done all it could to ensure there would be no transfer of the virus.

Despite the Grand Mercure not being a dedicated quarantine facility, Ardern said it did adhere to the same standards.

"We do everything we can around infection control. We have had Covid cases in Wellington facilities before, we maintain the same infection controls in any facility where people might have Covid regardless if someone has tested positive."

The Spanish-flagged vessel hasn't been fishing in New Zealand waters and was not operating on behalf of a New Zealand fishing venture, MPI says.

On the escalating situation in Fiji, where there are now more than 9000 active cases in isolation and 56 deaths linked to the current outbreak that started in April, Ardern said it was "devastating".

She has asked the Ministry of Foreign Affairs and Trade to contact officials there again and offer specific medical equipment that may be needed.

On issues with MIQ slots, Ardern said while demand was high it would inevitably drop over time. The Government was also constantly looking at ways to stop any "gaming" of the bookings system.