A health worker conducts a test at a Covid-19 testing centre in the suburb of Northcote in Auckland. New Zealand has had a dream run but must still keep up its guard. Photo: AFP / David Rowland

Health authorities have raised the Covid-19 alert to level 2 for Wellington, from 6pm on Wednesay until midnight on Sunday, after an Australian traveller who visited the New Zealand capital at the weekend tested positive on their return home.

The news comes only hours after New Zealand paused quarantine-free travel to New South Wales, following 10 new community cases in Sydney linked to the Bondi cluster.

Genome sequencing will determine if the Australian visitor carries the more infectious Delta variant, but the developments highlight how quickly things can change.

The emergence of more transmissible variants and the complacency of New Zealanders after 100 days without community transmission now provide ideal circumstances for a large outbreak.

New Zealand’s pandemic response and elimination strategy have drawn worldwide attention. At this point, the country remains one of few places in the world without community transmission since the end of February.

Countries like Taiwan and Fiji, once also success stories, have seen significant and rapid surges in cases and hospitalizations. What is happening in Taiwan, Fiji and other countries such as Vietnam should be a wake-up call for New Zealand.

Culture of complacency

Overseas news should serve as a constant reminder of New Zealand’s privileged position.

Calls on the government to make the NZ COVID Tracer app mandatory, at the very least in higher-risk places where large numbers of people meet indoors, will likely grow stronger now.

Low and decreasing use of the app make it harder to trace contacts, which leaves the country at greater risk of an outbreak, particularly if a more transmissible variant enters the country.

Variants and vaccination

The emergence of new highly infectious variants has already hit close to home with the recent outbreaks in Australia.

New variants are more transmissible and may also decrease the effectiveness of some public health measures. For instance, compared to the original Alpha variant, the Delta variant is 60% more contagious, making it harder to keep up with in terms of contact tracing. According to UK research, it is also twice as likely to lead to hospitalization.

New Zealand is relying on the Pfizer vaccine, but the rollout has been slower than in other countries. The good news is that preliminary research has shown the Pfizer vaccine to be 96% effective against the Delta variant.

The problem for New Zealand is that less than 10% of the population is now fully vaccinated and there is variation by region. If an outbreak were to occur with a more transmissible variant, it could spread easily, unless stringent public health measures are in place.

Vulnerability at the border

On the more positive side, the elimination of Covid-19 has allowed researchers valuable time to identify where vulnerable populations are (see map below) and model potential outbreaks. This helps inform responses to future outbreaks and prioritize vaccination.

Such research should help mitigate potential inequity, which has been evident in many aspects of the Covid-19 response around the globe.

New Zealand experienced eight known failures of its Covid-19 border control system between August and November last year, suggesting a systematic underestimation of risk. Since then, mitigation strategies have been put in place and border staff have been vaccinated, but that doesn’t mean the risk is zero.

One possible omission in making travel bubbles safe is the absence of pre-departure testing requirements for those travelling to and from Australia. Pre-departure testing is no guarantee, but New Zealand should consider extending it to all travellers, not just those from higher-risk countries.

While New Zealanders wait to be vaccinated, we need to do our bit and keep scanning in, turning on Bluetooth on the NZ COVID Tracer app, maintaining good hand hygiene and getting a test if required.

Acting quickly makes it easier to stop the chain of transmission and stamp out cases of Covid-19.

Matthew Hobbs is Senior Lecturer in Public Health, University of Canterbury, Lesley Gray is Senior Lecturer, University of Otago, Malcolm Campbell is Associate Professor in Health and Medical Geography; Deputy Director GeoHealth Laboratory, University of Canterbury.

This story first appeared on The Conversation website and is republished with permission. To see the original, please click here.