Research which has been funded by Air New Zealand has modelled the effect of selectively relaxing our border restrictions depending on each country’s Covid-19 risk levels, but experts have acknowledged its weaknesses.
The study is a model of how New Zealand could manage international arrivals by their country of origin and suggests we could offer quarantine-free travel or shorter stays in quarantine to arrivals from some less Covid-afflicted areas.
Professor Shaun Hendy, who leads Te Pūnaha Matatini’s Covid-19 modelling programme, said the framework outlined by the model was “impractical”.
Hendy said the methodology described in the paper was “sound, although the practicality of using reported fatalities in order to categorise traveller risk is questionable”.
“As the authors acknowledge, there is a lag between infection and death of around three weeks. Looking back to March 2020, if we had been using the system proposed by the authors, the lag between infection and death would probably have prevented us from escalating border controls fast enough to prevent the Alert Level 4 lockdown.
“Any approach to assessing risk from travellers, therefore, would need to be based on much more responsive indicators. Thus, as an exercise, the study is useful, but I don’t believe it presents us with a workable scheme for managing travel bubbles,” Hendy said.
He said the global situation had changed considerably since the paper was accepted as new strains of the virus have increased.
“This particular framework is impractical, however, and the specific conclusions drawn have been overtaken by global events."
Dr David Welch, senior lecturer at Auckland's University's Centre for Computational Evolution and School of Computer Science, pointed out the supposed model did not include vaccination, which will become an increasingly important part of how and to whom the border is opened up.
He said it was a “reasonable model” but he had not seen the details of the appendices.
Professor Michael Plank, a mathematical modeller at Te Pūnaha Matatini and University of Canterbury, said the research suggested five times more people could enter New Zealand than at present, which would increase the risk to the community by 20-50 per cent.
"This might not sound like a big increase in risk, but it means that breaches like the one that occurred at the Pullman Hotel last week will occur 20-50 per cent more frequently. This increases the chance of a community outbreak and the possibility that an Alert Level change would be needed to contain it.
“We will need a framework of this type to relax border restrictions once the world begins to emerge from the pandemic. However, Covid-19 is more prevalent now that at almost any point in the past. At the moment, we need to do everything we can to reduce the risk of importing Covid-19 into the community, not taking on additional risk,” Plank said.