New Zealand was lucky that the Ruby Princess stopped only temporarily here, Australia's chief medical officer Professor Brendan Murphy says.
The cruise ship stopped in Christchurch, Wellington and Hawke's Bay before returning to Sydney on March 19.
The ship is at the centre of multiple Covid-19 deaths across the Tasman.
Fifteen passengers from the Carnival cruise ship had died, and more than 650 people have been infected. They include passengers and other points of contact.
The cruise ship headed to New Zealand for a two-week cruise around the country.
The Ruby Princess berthed at the port in Napier on March 15, its last port of call in New Zealand before heading back to Sydney.
Its docking led to a cluster of Covid-19 cases in Hawke's Bay, including six in Gladys Mary Care Home in Napier.
Murphy told the Epidemic Response Committee today that Australia had many more cases than New Zealand, though two-thirds of the cases in Australia were from returning travellers and from cruise ships.
There were about 30 to 40 new cases every day. All returned travellers were being quarantined for the last two weeks, but a significant number of new cases continued to come from overseas arrivals.
Murphy said any clamour to relax the restrictions were still "premature", and there was no right answer to getting out of the pandemic without a vaccine.
Australia, as had New Zealand, had rejected the idea of a controlled outbreak, and Murphy said aggressive suppression was Australia's goal and he doubted "elimination" could be achieved in the long term.
Australia's "social distancing" had been in a "large part" similar to New Zealand's approach.
National leader Simon Bridges, who chairs the committee, said he had been told he needed a haircut, and he couldn't in New Zealand but hairdressers in Australia were allowed to continue to operate.
Murphy said people were told to work from home, but if they couldn't, they were allowed to go to work if they could remain physically distant. But gyms and theatres and beauty therapists were closed, and while there was huge debate about hairdressers, they were allowed to continue as the restrictions were likely to be in place for months.
Retail chains were allowed to stay open, but many chose to close, Murphy said.
Murphy said shipping malls were 80 per cent emptier than before the restrictions, but construction and manufacturing were proceeding. The latter sector had found to to maintain physical distancing than the former.
Murphy said the last thing Australia wanted was a relaxation of the restrictions leading to further outbreak. The use of apps to enhance contact tracing was needed before any relaxations, and there also needed to be a good supply chain of test kits, as well as sentinel testing to check wide community transmission, which he said was still some weeks away.
He said, though, that most school outbreaks had been adult-to-adult, and getting schools back and running was on the agenda.
Murphy said some states with bigger outbreaks were considering greater business closures, but Australia went for a two-person gathering restriction instead.
But if we were pursuing a total elimination strategy, that's the situation where you might go a bit harder for big longer - that's a debate we have to have, but at the moment there's no pressure."
Australia would love too achieve elimination, he said, but he wasn't sure how realistic that was.
Asked about the possibility of open borders between New Zealand and Australia in light of different approaches, Murphy said there wasn't a large difference in strategy with New Zealand, and time will tell if either country can completely remove transmission.
Murphy said the public health recommendations were that physical distancing could be in place for several months, which was why major gatherings, pubs and clubs, cinemas and gyms were all shut. Construction, manufacturing and retail would have followed if the outbreaks had been worse.
"The feeling in the National Cabinet was we would like to keep some of those core activities going, and clearly if things got worse or do get worse, we would go harder."
He would not be drawn on whether New Zealand should allow more construction, manufacturing and retail, saying it depended on New Zealand's circumstances and it was a decision for the New Zealand Government.
'We'll go harder than NZ'
Murphy said until a vaccine was ready, the level of vigilance needed to "be huge" and further outbreaks were always possible. An "illegal dinner party of medical workers" was responsible for a recent outbreak in Australia, he added.
"It's a long haul, with measures in place that are pretty significant that you can tweak a bit from time to time, but nothing will really beat having a really broad public health response. The evidence that if you got hard late, which the UK has done, you can see what carnage you suffer on the way through. As soon as we saw significant community transmission, we felt we did have to go hard. Our 'hard' is very different to someone else's 'hard', but it is very disruptive. We may not have gone as hard as New Zealand, but we will go harder if necessary."
He said surveillance testing - collecting information to see where coronavirus is present in the population or among certain demographics - and the use of smartphone technology and physical distancing would continue to be the "new normal", and festivals would likely continue to be banned for the foreseeable future.
He said the TraceTogether app, which is used in Singapore and is being considered by New Zealand to enhance contact-tracing, was also on Australia's radar.
Australia had less stringent measures than New Zealand and the Australian Government had not wanted to close schools - but parents had stepped in and stopped sending kids to schools.
Kiwi health boss on how NZ compares to Oz
Asked about the less severe lockdown in Australia, particularly in construction, manufacturing and retail, Director General of Health Ashley Bloomfield said there was more "strikingly similar" in the two approaches and Australia was probably at alert level 3.5, depending on the state.
He added that Australia was prepared to "go harder" if necessary, and New Zealand had decided to go "a little harder to start with", but he was watching Australia to inform the New Zealand Government about how to move forward.
Bloomfield said no decisions had been made on whether to ease restrictions on certain sections of the economy, and things wouldn't be the same at alert level 3 or even 2 because physical distancing measures would "continue to be absolutely essential".
"Whatever level we find ourselves in in four or six weeks, there will be some fundamental things about physical distancing, the ability to contact trace - those will be almost like a new baseline."
He added that the economic activity will likely be eased slowly, with a close eye being kept on how that goes.
Australia had allowed more small food stores to stay open and construction workers to keep hold of their livelihoods, but Bloomfield said the message not to go out except for something essential was the same message in both countries.
Asked about whether New Zealand could have had a looser lockdown and still achieved what Australia had done in suppressing outbreaks, Bloomfield said it was not possible to say.
"It's different in each country because the pattern is different in each country."
Bloomfield said over 6000 samples can be tested a day, and he pushed back on the suggestion that comprehensive contact-tracing capacity would not be ready in time for lockdown to be lifted from next Thursday.
Bridges said there didn't seem much happening at the moment with sentinel testing, which Health Minister David Clark said would be rolled out "imminently" on March 18.
Bloomfield said more than 66,000 tests had now been done and there was a good regional spread of tests. "That's giving us a very good picture of Covid-19 and/or the spread, where it may be around the country."
He added sentinel testing would be rolled out soon.
Bridges said there were gaps in the Ministry's information about the days taken for a test result and the time taken for contact-tracing - key factors in whether the lockdown can be eased.
Bloomfield said the manual system had been upgraded in recent weeks and that information will be available soon.
Next week he would be able to talk about the time taken from when people develop symptoms to when they are tested and how long they've been in self-isolation.
Bloomfield said a shortage of nasal swabs was not a factor in the declining trend in the number of new Covid-19 cases, adding that a throat swab can be used in cases where a nasal one was unavailable.
Asked if the Maori population had not been tested enough and there was a risk of undetected transmission, Bloomfield said 14 to 15 per cent of total testing had been done on Maori and there was a low positivity rate (the rate of positive tests in terms of the number of tests done).
Asked whether the 700 new daily arrivals into rest homes and aged care facilities should all be tested, Bloomfield said they should all be put into self-isolation and there was a low threshold for testing. An independent audit would also look at the rest homes where there have been outbreaks so that lessons can be learned.
Labour MP Kiri Allan asked about the vulnerabilities around rural communities, including Te Ti Rawhiti, and Bloomfield said restrictions into and out of those areas were being considered.
Bloomfield said the rationale for going harder - and imposing more restrictions than Australia - was to come out of lockdown as quickly as possible.
"I can't say. I'm sorry, I'd love to be able to say that," Bloomfield said when asked about whether New Zealand was likely to go back into alert level 4 again once the nationwide lockdown was the lifted.
"We will learn from each other and will continue to do so," he said of Australia's experience.
Bloomfield said New Zealand and Australia had the same goal and the approaches were "variations on a theme".
The declining trend in the number of new daily cases was a reason for more optimism, and Bloomfield said the decline was faster than expected - but there was no room for complacency.
Bridges pressed Bloomfield on PPE, noting that there appeared to be a disconnect between reality and the Health Ministry's line that PPE was available for all those who needed it.
"Doesn't that show more progress still is needed?" Bridges said.
Bloomfield said the process was "not perfect" and he was happy to receive correspondence showing where access to PPE was failing.
Australia 'an enigma' on coronavirus – expert
Otago University Professor and epidemiologist Sir David Skegg cautioned the committee about comparing Australia to New Zealand.
He said Australia was a "bit of an enigma", even though the number of per capita cases in Australia was similar to New Zealand.
"If you look at the harder end points, in terms of recurrence of disease, they have a lot more deaths than we do ... if you look at hospitalisations, Australia had 378 people in hospital. New Zealand has 15."
That amounted to five times as many people in hospitals in Australia, accounting for the difference in population size, Skegg said.
Skegg said it was "most impressive" that contact-tracing in Australia was down to two to three days - Bloomfield had not been able to say how many days it was taking in New Zealand.
Australia was at an alert level of 3 to 3.5, but that was expected to continue for up to six months, but Skegg said New Zealand could achieve elimination to the point that the country would not need to go back into nationwide lockdown after four weeks.
"I don't think we should apologise for trying to get a better outcome."
He said a lockdown on its own was never going to be enough. "It's like pressing the pause button on your device."
As soon as the lockdown is lifted, the epidemic will take off again unless there was widespread testing - "we have made a lot of progress in that area" - as well as rapid contact-tracing, where "a lot of work is needed" until we reach Australia's level.
Skegg said it was foolish to presume a decline in new cases was enough to show the virus was being eliminated, and more testing data was needed to be more confident - especially among more at-risk groups.
Sentinel testing was essential before "we have reached the point where we can take our foot off the brake", and there was still no sign of when that would start taking place in New Zealand.
He noted the 8.5 per cent positivity rate in Queenstown, and special surveys of essential workers would be needed there before any confidence could be had about the spread of Covid-19 there.
"I am worried that the Cabinet will have to reach a decision as early as next Monday," Skegg said, in light of the lack of information about contact-tracing and the unlikelihood of survellance surveys being carried out and completed by the end of the week.
Without that information, Cabinet will be playing "Russian roulette" with New Zealanders' lives in deciding on Monday whether lockdown should be lifted, Skegg said.
Prime Minister Jacinda Ardern and Bloomfield have previously said that an app to enhance contact-tracing did not need to be ready before lockdown might be lifted.
Bloomfield has also pushed back on the need - proposed by infectious diseases specialist
Dr Ayesha Verrall - for close contacts of 1000 cases to be traced in a day. Bloomfield based this on the fact there are fewer than 1000 active cases in New Zealand now.
Skegg said contact-tracing would be so important to be able to isolate and contain any outbreak post-lockdown.
He said New Zealand was in its third week of lockdown but still was nowhere near where it should be in terms of contact-tracing.
National MP Paul Goldsmith said Australia had shown that lockdown could be eased and the number of new cases would still be "manageable", and Skegg New Zealand could have similarly looser restrictions but only if it had more rapid contact-tracing in place - which Australia currently has.
Skegg said New Zealand's efforts to control Covid-19 didn't need to be at the expense of other people's healthcare. Keeping hospitals at 50 per cent capacity was appropriate for alert level 4, but "I don't see why that should continue ... if we're successful in eliminating this".
Skegg said Australia would need to hold its own lockdown for at least six months, possibly 18 months. "The countries that have not succeeded in controlling this disease - in a few months, it will probably be 100 countries - I would be very surprised if we're going to do worse economically because of the measures we're taking in the medium-term."
He said he would love to see "some transparency" about the criteria for coming out of lockdown, and an independent advisory committee including public health experts, academics and business leaders should be set up to advise the Government.
Referring to Australia's much higher hospitalisation rate, Skegg said it was an enigma because, like New Zealand, Australia had a high rate of testing, a high proportion of positive cases linked to comparatively healthy travellers returning from overseas, and was coming out of a summer.
"I can't really explain it."
He said the details around the alert levels were not "set in stone like the ten commandments", and the measures at levels 2 and 3 could be different on the way down than on the way up.