His comments come as two more top Auckland schools, Western Springs College and Pukekohe High, and two of New Zealand's best-known companies, Sky City and Sky TV, have been caught up in the Covid Delta outbreak - with positive cases of students and staff.
There are now seven schools caught in the pandemic, with Avondale College, McAuley High School, Northcote College, Lynfield College, and De La Salle College also hit by cases.
And an Auckland Fisher & Paykel Healthcare worker has tested positive for Covid-19. The person worked nights in the East Tamaki facility and is now in managed isolation.
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In a statement this morning, a Fisher & Paykel Healthcare spokesperson said they were following established contact tracing processes and had been working with public health authorities to notify anyone who may have had contact with the person.
"Our people have had early access to COVID-19 vaccinations, and we have extensive on-site safety measures, such as rapid saliva testing and Bluetooth contact tracing cards, to minimise the chance of transmission at our facilities."
Prime Minister Jacinda Ardern yesterday warned cases will continue to rise into the next week - and an extension of the Auckland lockdown, at least, seems inevitable.
Sky TV and Sky City casino are working to identify close contacts after they each had a worker test positive, while Western Springs College and Pukekohe High have become the sixth and seventh Auckland schools hit by cases.
The developments come as more than 10,000 close contacts - from Auckland and Coromandel to Wellington and some parts of the South Island - have now been identified in connection with New Zealand's so-far 51 confirmed cases, 45 of whom are in Auckland and six in the Capital.
There are also around 200 visits to 165 locations of interest, including four in three central North Island towns - areas where a Wellington pair had stopped while driving back to the Capital after visiting Auckland.
Te Pūnaha Matatini Covid-19 modeller Professor Shaun Hendy said based on their modelling they were still predicting about 100 cases to have been circulating before lockdown.
All of the cases so far had been linked to the cluster before the lockdown began.
Hendy said he expected numbers to start peaking early this week, but they wouldn't know how effective the lockdown was at containing the spread until next weekend.
"The big unknown is how effective level 4 restrictions are with Delta. We know it worked well last year but this is a more transmissive variant now so we expect the lockdown to be less effective."
Hipkins said it was too early to tell how plans might change.
"We're still aiming for elimination at this point and I think we do need to give it a really good go and see if we can drive it out again. It's absolutely our number one priority in the moment it seems so really what we're focused on, but we also need to drive up our vaccination rates and we're really focused on doing that.
"We've recalibrated our vaccine campaign so that it can continue despite the level four lockdown and if anything we're doing more vaccinations now than we wouldn't be had not been for the lockdown.
"So we're very focused on thinking and making sure that we're preparing for a different kind of a future but at this point we don't really know what that will look like.
"I think if you look at our overall risk profile and what we've been doing to manage risk. You know that we've got a really good robust managed isolation for people coming into the country in the pre-Delta world.
"Now, in the Delta world though it just highlights how quickly the virus can spread. Someone can have infected a number of other people before they even make it to managed isolation so the very act of coming through the airport potentially becomes even more risky than it was before.
"So we have to think really carefully about are there more things we can do to reduce risks. Now, the thing is we've been doing that all along so we've explored most avenues already. There aren't a lot of extra gains we can make here.
"At some point we will have to start to be more open in the future and the Prime Minister set it out a few weeks ago for us. It will include making sure that we've got very high vaccination rates, the more people that get vaccinated, then the more options we're going to have."
Long delays for Covid tests
Hipkins said a six-hour wait for testing was "a reality", given how high the demand is with so many locations of interest.
But there were undisclosed testing locations where people who needed to be tested immediately could do so.
"The scale of infectiousness and the speed of the virus has put our system under strain."
Hipkins said there was no option for the Government to have more Pfizer vaccine supply by providing an incentive payment.
There has been speculation that paying an extra $40m to $50m could have seen higher volumes of supply arrive in New Zealand earlier.
"That was never presented to us as an option," Hipkins said.
"The only way to increase volume would have been use other vaccines in addition to Pfizer."
Even then, the purchase agreements with the other three vaccines that the Government has didn't expect arrivals of those supplies until the second half of this year. They also couldn't arrive before Medsafe approval for their use.
Hipkins conceded that more ICU-capable beds didn't mean more ICU capacity if there wasn't enough highly specialised ICU staff.
"You can't just magic up extra healthcare workers.
"We are bringing in healthcare workers across the border, but every country that's dealt with this has had to adjust their ICU settings, including lower ratios of staff where there are significant numbers of Covid patients."
Some nurses have been upskilled to take some pressure off ICU staffing levels, he said, but they were not ICU specialists.
"Hospitals have contingency plans to convert general wards into facilities to cope with Covid-19 if we get to that point."
A large outbreak would put the health system under pressure, Hipkins said.
"No amount of planning will be able to completely alleviate that."
ICU doctor Craig Carr, who is the New Zealand regional chair of the Australia NZ Intensive Care Society, told the Herald earlier this week that ICU capacity - including ICU staff - hadn't increased in the last 18 months.
"We now have more equipment compared with 18 months ago, but we actually have very few extra staff, and in some instances, we've got fewer staff," he said, adding he was speaking in a personal capacity.
"Actual resourced bed capacity on a day-to-day basis, in terms of a bed with a nurse and a ventilator and all the monitors - that has not risen, to my knowledge, in the last 18 months."
Last year New Zealand ranked near the bottom of the OECD for per-capita ICU capacity, but since then the Ministry of Health says the number of available ICU-capable ventilators has more than doubled.
In May last year, as the country was coming out of its first lockdown, a Ministry of Health paper found there were 334 ventilators and 358 ICU beds.
There are currently 284 fully staffed ICU beds across public hospitals, and the ministry says there are 629 ICU-capable ventilators, with 133 in the national reserve if required.
But capacity isn't necessarily increased without additional ICU staff, Carr said.
The Ministry of Health does not hold data on ICU nursing staff, but noted a Nursing Council survey of nurses who said they worked in "intensive care/cardiac care" as either primary or secondary work.
There has been little movement in this number of nurses, with 2524 such nurses in the year to March 2020, and 2550 nurses this year.
DHBs last year were asked to have surge capacity for 550 ICU-capable beds, but Carr said that wasn't the same as business-as-usual ICU beds.
"You get to the point of what Italy had with lots of patients on ventilators, but they weren't being looked after by an ICU nurse or doctor.
"Clearly the patient's still got a chance at life, but it's not as good as if they had an ICU and doctor to engage in their day-to-day care."
That meant a level 4 lockdown was the right response for Delta cases in the community, Carr said.
Cases set to peak this week
Professor Michael Baker says the Delta outbreak should peak this coming week and despite a large number of exposure events, "I am sure we will beat this".
Baker spoke to Francesca Rudkin on Newstalk ZB this morning and said there were a huge number of exposure events, and some could end up being "superspreaders", with large numbers of people infected.
"Given the huge number of exposure settings and that some of these were quite high risk indoor environments, we are obviously expecting quite a few more cases," said Baker, an epidemiologist at the University of Otago.
"The good news is that these infected cases were only in the community for a short period of time, because we do know when the virus first arrived in New Zealand ... that really is good news because it limits how many times the virus will go through its reproduction cycle, and we know that each case on average may infect five or six others, but it only had 7 to 10 days in the community to go through those cycles. So it won't be a huge outbreak, fortunately."
The Delta variant is much more infectious but had a shorter incubation period, Baker said - around two, three or four days. That meant new cases should come through more quickly.
"We should see it peak very soon, actually - just this week."
While it could be unsettling to see more and more cases confirmed each day, Baker said New Zealanders should take heart in the fact Delta community outbreaks had been contained, including South Australia and Queensland.
The New Zealand Government had done the critical thing and imposed a strict lockdown soon after the first case was detected, he said.
"I am sure we will beat this."
An important factor in how quickly the outbreak could be contained would be how many people were infected after people with the virus attended indoor events like church services.
"I know when I looked at that growing list of places of interest ... my heart sank, because it included just about every high risk indoor event you can think of. But, again, it just comes down to whether there was an infectious person at one of those events or not."
Baker was impressed by the levels of vaccination that had been sustained, despite the lockdown and need to also ramp up testing to record levels. He thought the daily vaccination rate could improve even further, given there was no longer a supply problem.
Asked about weaknesses in our lockdown, Baker said New Zealand's was about the strictest in the world, but still had gaps. One was essential workers who were at higher risk. Another was young people with large social networks and who might be less inclined to follow the rules.
When asking people to observe the lockdown restrictions Prime Minister Jacinda Ardern has often pointed to the ongoing Delta outbreak in New South Wales.
Baker said elimination "may have" passed NSW by, and they could now be looking at a suppression strategy.
That was much tougher on the population, he said, with ongoing restrictions and more illness and death. Even in the United Kingdom, with high vaccination rates, there were still 800 people ending up in hospital with Covid-19 every day, and about 100 dying.
Baker said it was essential for New Zealand to continue with the elimination strategy until we had high vaccine coverage. By early next year a discussion would be needed about whether that strategy should be continued, he said, or switched to a suppression approach.
"I don't think we know enough yet about this virus to know what to choose."
