This morning's restart of the travel-bubble with New South Wales has the thumbs up from an expert in disease spread modelling, who says the pause was wise, and it's now time to go ahead.
But an Australian epidemiologist said the travel pause was too soon, and New Zealand should be slower on the draw next time round.
Photo: 123rf.com
The three-day travel pause in quarantine-free travel between New South Wales and New Zealand resumed as the clock ticked over from midnight this morning, despite restrictions extended in Greater Sydney for a further week.
Travel from New South Wales to New Zealand was paused on Thursday after two men tested positive for Covid-19 in Sydney, where authorities are yet to find how they became infected.
University of Canterbury professor Michael Plank said the pause gave experts time to investigate and assess the risk posed by the new cases. But, the specialist in modelling complex biological and social systems is satisfied those investigations showed re-opening to two-way travel is warranted.
"We just needed to make sure that it wasn't a major outbreak" - University of Canterbury professor Michael Plank
"They've done a lot of testing in Sydney over the last few days, and the fact that they haven't found any new cases gives us confidence that we're not looking at a big new outbreak. So, although new cases might trickle in over the days ahead, provided they're related to that same cluster it's nothing to be alarmed about.
"So, really the concern was that we could have been looking at a large number of hidden cases, and it seems that's not the case now. If it's one or two cases here or there the risk is still really very very low with the bubble, we just needed to make sure that it wasn't a major outbreak."
University of Canterbury professor, Michael Plank. Photo: Supplied.
Travel arrangements between different countries, states and regions have spotlighted the different approaches being taken to risks from the virus. So far New South Wales had not been as willing to impose strict lockdown measures when new isolated cases arose, compared to New Zealand.
Plank said there was likely various factors contributing to the different reactions, including different tolerances of risk or confidence in contact tracing systems.
"The approach that we've taken [in New Zealand] has been fairly consistent - that if a case pops up with no link to the border, that's when you need to think about alert level changes and that kind of thing.
"I think that's the right approach for New Zealand ... other states will have slightly different approaches, but it's worked for us so far."
New Zealand shut travel down too soon - Melbourne expert
"It is tricky decision-making" - Epidemiologist Tony Blakely
Melbourne-based epidemiologist Tony Blakely said pausing the travel bubble was premature.
"It is tricky decision-making. I suspect if this was to happen again next week New Zealand would not close the border. I think it was [premature], but that's with the benefit of having seen this happening many times within the states and territories borders over here."
University of Melbourne professor, Tony Blakely. Photo: Billy Wong/University of Auckland
Australians generally felt the two Sydney community cases were part of the new "business as usual," he said.
"These things pop up and happen and go away. It is challenging that we haven't found the link here. We need to remember that only 20 to 30 percent of people with Covid are actually the ones who spread it a lot.
"So we have to assume that the person who is the missing link here just happened by some small chance to pass it on to this couple that then presented, but the chains of transmission have died out. We don't know that yet, it will take a few more days, perhaps another week with no cases to be confident that that chain of transmission has petered out."
There were less disruptive ways to handle the risk caused by unexplained community cases, instead of a 'blanket ban', Blakely said.
"For example, just requiring or requesting people who've been in the contact areas - who've been in the same shop or the same places as infected people - to not travel. To ask people if they are travelling to go into isolation for a couple of days whilst the the contact tracing is sorted out.
"Everything with Covid is about risk reduction, so there's nothing that's going to be 100 percent successful - we're talking about 99.99 percent."
The handling of Covid-19 cases in the community by both New Zealand and Australia was working, but there was also some luck involved, he said.
"But we've learned that you just have to manage this risk. You can't shut down with a lockdown based on one case.
"We did that for a while in Australia when Queensland had cases around Christmas time. But we've learned that you don't need to do that, even with the new variants, as long as you've got really good contact tracing and you've got public that's prepared to put on the masks to reduce the risk.
"We're all learning how this is working as it unfolds, and we're going to have 6, 12, 18 more months more of this, until vaccinations gets us out of the woods."
Restrictions in New South Wales were "progressive", he said, and involved trying to cut risk where possible, without interfering with businesses.
"It's impressive I think, they're looking at the evidence ... they're asking people not to do those types of activities where there's essentially no economic cost ... and so far it's worked.
"One of the more interesting restrictions is that front-facing staff in shops and places like that are required to wear masks, but some of the patrons are not. Which is really starting to push the line of risk reduction here. The reason being that a front-facing staff member is going to see a lot of people in a day."
People had also been asked not to sing indoors, because of an increased risk of transmitting aerosolised virus particles.
Reducing the risk for New Zealand
Plank said cases of Covid-19 in New Zealand had so far occurred in such a way that for every 200 cases caught in managed isolation there had been one community outbreak.
"Historically that's correct, looking at the statistics over the last year or so. But we have made improvements to our border system and our managed isolation and quarantine, so hopefully over time we can reduce that risk.
"Vaccinating our border workers will be a big step in reducing that risk. So hopefully we can minimise this going forward, but we do have to be prepared that this could happen again and we might see more border-related outbreaks in the future."
The number of people arriving into manage isolation who have tested positive for Covid-19 had been reducing, which he put down mostly to closure of the border to travellers coming from India, from 11 April, due to ballooning case numbers there.
Community cases where the path of infection was not able to be traced were "frustrating", but highlighted the need for community vigilance outside of border and managed isolation facilities, he said.
"We've had outbreaks here, and in Australia as well, where we've never managed to find the root cause of it, or there's a missing link that we've never been able to track down ... it would be nice to know where it came from. But at some point you do have confidence that the outbreak's contained and that you can move on."
Combating Covid-19 successfully relied on several different layers of surveillance, care and protection, Plank emphasised.
"We have to remain vigilant, we have to keep up our testing rates, we have to keep scanning - doing all these things. Each one is one layer that just helps us catch these outbreaks, and make sure we catch them before they get too big."