With the opening of a quarantine-free travel corridor between New Zealand and Australia this week, it’s easy to forget COVID-19 is still spreading globally, faster than ever, with more than three million deaths recorded worldwide.

Within a day of the travel bubble opening, a fully vaccinated border worker who cleans planes coming from countries with high rates of COVID-19, tested positive and was transferred to a quarantine facility.

Such cases show why it remains absolutely essential to maintain strict border measures to keep the virus out of the trans-Tasman bubble.

Since January 1 2021, 397 international arrivals in New Zealand have tested positive for the virus. Most have been contained in managed isolation and quarantine (MIQ) facilities.

Cases detected at the border


But we have seen some cases leak out from the border. These fall into two main categories: returnees leaving managed isolation while still infectious and frontline border workers becoming infected with the virus.

To consider the effectiveness of various border policies, we pulled together data on transmission of COVID-19 and rates of false negative test results into a mathematical model. The research, published today, allowed us to quantify the risk of community outbreaks under different quarantine and testing regimes.

Outside a quarantine hotel
People returning from countries other than Australia have to spend 14 days in isolation.
Getty Images/Phil Walter

Managing risk from international arrivals

Our research shows that a 14-day stay in managed isolation, with tests on day three and day 12, is highly effective in stopping international arrivals from re-introducing COVID-19 into the community. Under this regime, most border cases are either detected and isolated until recovery, or are no longer infectious by the end of their 14-day stay.

By comparison, reducing the time spent in managed isolation would greatly increase the risk. We found that with a five-day stay, around 25% of cases would still be infectious when they entered the community.

Given recent arrival numbers, this would mean multiple border-related cases in the community every week. Sooner or later a major outbreak like Auckland’s August cluster would be inevitable.

Read more:
Genome sequencing tells us the Auckland outbreak is a single cluster — except for one case

Managing risk from frontline border workers

Border workers in the arrival hall.
The virus can leak into the community if border workers become infected.
Getty Images/Paul Kane

The research also looked at various testing regimes for frontline border workers. We found that weekly routine testing roughly doubles the chance an infection will be detected while it still has a clear link to the border.

The recent case of a worker at the Grand Millenium MIQ facility was an example of this.

When we find a case with a clear link to the border, typically only a small number of people are infected. The outbreak can usually be contained through contact tracing without the need to raise the alert level.

On the other hand, if border workers are not tested regularly, it increases the chance the outbreak could spread into the community. This means a large number of

It launched with a presidential escort and the promise of rare international travel to a postcard-perfect tropical island, but the Taiwan-Palau travel bubble has deflated after just a couple weeks, with Taiwanese bookings dwindling to single figures.

Travel agents, consumers and health authorities have blamed the high cost of the tours and the Taiwanese government’s strict rules for returning travellers.

The “sterile corridor” of bilateral tourism guaranteed travel between the two archipelagos, which are both otherwise closed to all tourists, on strictly managed, twice-weekly package tours.

The inaugural flight, packed with nearly 100 passengers including Palauan president Surangel Whipps Jr, boded well, but this week China Airlines announced it had cancelled an upcoming flight from Taipei after just two people booked tickets. The airline told the Guardian it was constantly assessing the situation but it couldn’t guarantee further cancellations.

To go on the Palau holiday from Taiwan, tourists must make several health declarations, pay for Covid tests, and not have left Taiwan in the last six months. Upon return they had to complete 14 days of “self-health management”, including five “enhanced” management days banned from public transport and spaces. On Wednesday health authorities announced it was dropping the enhanced requirement, and agencies are hoping it’s enough to restore interest.

One of the six agencies contracted to run the tours, Phoenix travel, told the Guardian they’d had “sporadic” individual bookings and inquiries about future tours, “but the momentum is not as good as expected”.

“The fare is higher than normal, plus the cost of two PCR tests, and the inconvenience of health management after returning home are the reasons why most travellers maintain a wait-and-see attitude,” the spokesperson said.

Taiwanese passengers pay between $2,100 and $2,800 plus associated costs for the group tour which runs for fewer than eight days, keeps the tourists away from crowded locations and local people, and doesn’t allow for autonomous activity.

On Wednesday evening Whipps welcomed the easing and said returnees who didn’t show signs of fever and hadn’t been in the presence of anyone who did, could “go about their daily lives as usual”.

Two-dogs beach in Palau’s Rock Islands.
Two-dogs beach in Palau’s Rock Islands. Photograph: Richard Brooks

Whipps also said costs had also been decreased, but did not detail by how much. He claimed the presence of Tropical Storm Surigae had also affected bookings, but that the two governments were working closely together to improve the bubble.

He said his office had been “assured” that the next scheduled flight on 21 April would have more passengers. The Guardian has contacted the Taiwan government for confirmation of the changes and comment.

Palau has recorded zero cases of Covid, and is on track to have 80% of its population vaccinated by the summer, while about 90% of Taiwan’s 1,062 cases were recently arrived people in quarantine, and there is no community transmission.

The travel bubble was hailed as a lifeline for Palau’s tourism industry, which contributes almost half of its GDP, but had been completely stalled by the pandemic. Taiwanese made