Trans-Tasman bubble: Why it may lead to more Covid-19 cases

Tuesday, 23 March 2021

Following Monday's Cabinet talks, Prime Minister Jacinda Ardern says Cabinet will reconvene to discuss trans-Tasman bubble on April 6.

EXPLAINER: Prime Minister Jacinda Ardern is set to announce the opening date of a travel bubble with Australia.

The bubble would allow people from Australia to come to New Zealand without a two-week stay in a managed isolation hotel.

Free travel from Australia would help reinvigorate a stagnating tourism industry, providing the country with a much-needed economic boost.

However, it may also have an inadvertent side effect – it may well open up managed isolation and quarantine (MIQ) spots to returnees from countries where Covid-19 is common, and this has some experts worried.

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Covid-19 Minister Chris Hipkins has acknowledged the Government was aware of the risk and was considering what the future of MIQ would look like.

The current situation

Right now, the borders are only open to a handful of groups including:

Citizens and permanent residents.
Partners or dependent children of citizens or permanent residents, when the visa is based on this relationship.
Australian citizens or permanent residents who normally live in New Zealand.

There are a variety of other “critical” reasons that allow people overseas to apply to travel to New Zealand, including work and study.

Since early last year, there have been about 1200 imported cases of Covid-19 from 89 different “countries of departure”.

Nearly 900 imported cases are from 10 countries, with three standouts – the UK, US and India.

Only 35 imported cases originated in Australia. This is a modest total as about 40 per cent of those in MIQ arrive from across the Tasman.

There have been 93 imported cases in the last 30 days. Almost half of these were from India, which saw about 250,000 new Covid-19 cases in the week from March 15 to 21. That was up 100,000 on the previous week.

There were seven cases from the US. Interestingly, there have only been two cases from the UK.

A woman walks past the barriers outside the Grand Mercure Hotel in Britomart, Auckland, New Zealand.

The reason for the drop off in cases from the UK and US is unclear. Thirty days is a relatively small sample size, but there has been a significant drop off in Covid-19 cases in both countries, coinciding with rapid vaccine roll-out.

There have been no cases from Australia in that period. The last was in January. It’s clear the risk of people arriving from Australia here with the virus is very low.

In total, about 125,000 people have passed through MIQ facilities since March last year. Right now there are 4500 MIQ rooms available and about 4100 of these are occupied.

The rooms are booked up until mid-June.

The danger

The danger, epidemiologist Professor Michael Baker explains, is that newly available rooms could be taken by returnees from Covid hotspots, which in-turn increases the risk of outbreaks.

See how the UK variant compares to the original Covid-19 strain.

There are 4500 MIQ rooms. Right now, Australian arrivals occupy about 40 per cent (or 1800) of those. (In reality, it's slightly fewer, as there’s always some spare capacity in the system).

Introduce a travel bubble and all of those “Australian rooms” are, in theory, up for grabs.

Travellers from anywhere other than Australia have a greater chance of contracting Covid-19, be it from the country they are living in, from others in transit, or from airports they pass through.

“If we just open up that spare capacity, and it gets filled up in the proportions we’re currently seeing, then yes, we can expect a lot more cases arriving at our borders,” says Covid-19 modeller Professor Michael Plank.

It’s not exactly clear what the government will do with that extra capacity when (or if) the trans-Tasman bubble goes ahead. But even if there wasn’t sufficient demand from citizens or residents, it would be tempting from an economic perspective to allow a greater influx of essential workers or international students, for example.

Hipkins, however, said at Tuesday's press conference the 1800 “Australian rooms” would not necessarily all be made available to other returnees.

That said, even if a small percentage of the Australian capacity in MIQ is made available, that's still extra room for returnees from Covid hotspots.

So, say the 1800 rooms are freed up, and 450 of those are subsequently made available, that still increases the potential for new cases on our shores. Travellers from Australia simply aren’t bringing Covid-19 here right now.

The solution

“I think we need to make sure we don’t just have a massive increase in the number of people coming in from countries where the rate of Covid-19 is very high,” Plank says.

On this Baker warns: “We have to think about the unintended consequences.

“We have to understand the risk to New Zealand increases with the number of people coming from those countries [with numerous cases].”

On Wednesday, Hipkins pointed out the Government will need to increase the MIQ contingency capacity it holds, just in case something was to go wrong while the trans-Tasman bubble is operational.

This may mean it keeps some, or even all, those “Australian rooms” available as an insurance policy if it suddenly needs to isolate Kiwis, stuck or returning, from Australia. That should, in theory, decrease any increase in risk.

The vaccine roll-out to border workers should also offer further insulation against outbreaks.

It would appear at first glance to be a concern that the MIQ worker that tested positive on Monday been vaccinated.

However, it's important to remember this is only one case. And recent data from the UK suggests the Pfizer/BioNTech vaccine not only reduces the risk of serious illness, it offers protection against transmission.