The NZ Covid Tracer app remained one of New Zealand's most crucial tools in fighting Covid-19, with modelling showing the time it took for officials to track down and isolate contacts was the biggest factor in keeping an outbreak under control.
Data expert Dr Andrew Chen said the leap in numbers showed this week's news had driven a behaviour change around using the app.
"We still have a long way to go in terms of getting a good level of participation in the system," said Chen, a research fellow with Koi Tū: The Centre for Informed Futures at the University of Auckland.
"We want to see 60 to 80 per cent of eligible adults participating - we should ideally be seeing four to six million QR codes a day, and probably about two million people in Bluetooth tracing - but it's good to see the numbers trending up."
He was confident that the number of Bluetooth activations would keep going up as, once people turned the function on, they'd leave it active.
"It will be really interesting to see if we can convert this current wave of activity into longer-term behaviour change," he said.
"That'll be up to the Ministry of Health to look at things beyond an advertising campaign, and at things like more engagement with businesses to make sure they have QR codes very visible, and that they have staff encouraging people to scan."
Chen thought more positive incentives for using the app could help as well.
"I believe the Ministry of Health has been investigating these and there might be some in the next version of the app - just things like visual reminders or congratulatory messages."
Some businesses have come up with their own incentives one Auckland steakhouse was offering diners who used app a 5 per cent discount, while a Nelson cafe was giving out free biscuits to scanners.
Last week, a new study co-led by a Otago University researcher suggested the key to getting more uptake was fostering trust and buy-in among customers, rather than threatening not to serve them if they didn't sign in.
