The latest NZ Covid Tracer app stats from the Ministry of Health show we're still slackers at scanning posters, but more and more of us are turning on Bluetooth.
For Saturday, January 23, some 286,646 people scanned at least one QR code poster.
But the number who had switched on the app's Bluetooth automated contact-tracing feature - introduced ahead of Christmas - had reached 605,751.
It will now be somewhere well above that level.
At today's 1pm briefing on the Northland case, Covid-19 Response Minister Chris Hipkins said had been advised of a surge in Bluetooth enablement over the past 24 hours.
The MoH stresses that people need to follow both measures. Poster scanning tracks where you go, whereas the automated Bluetooth feature tracks who you have been in close contact with (with a number of features to protect your privacy - watch the clip below).
But the stats indicate that - at least up to the point of the Northland case - many were skipping scans.
Earlier, Dr Andrew Chen, a researcher with Auckland University's Koi Tū: The Centre for Informed Futures, told the Herald that while Bluetooth enablement is off to a good start, it's still at only about a quarter of the required level.
"But based on the modelling work done by Te Pūnaha Matatini [which draws on research from multiple universities and agencies], I think we need at least 2 million people participating to have more confidence that this data will be useful in the unfortunate event of a further outbreak in NZ, Chen said.
At the current rate of around 5000 people enabling Bluetooth per day (prior to the 24-hour surge Hipkins alluded to today) it would take until nearly the end of the year to hit the magic 2 million mark.
"It's heartening to see the number of devices participating in Bluetooth tracing climb over the last month," Chen says (Bluetooth was added on December 11).
"It has been pretty steady, suggesting that it is slowly spreading through mouth-of-word rather than there being a big event or advertising campaign driving change suddenly."
A spokeswoman for the Ministry of Health said the new Bluetooth feature had been promoted as part of the "Make Summer Unstoppable" campaign.
Chen says the addition of Bluetooth was swamped by other news ahead of Christmas before people switched-off and went to the beach, enjoying a Covid-free summer. There's scope for dialling up the messaging again.
The Ministry of Health spokeswoman says, "There will be a lot more activity encouraging QR code scanning and Bluetooth use over the next few months."
For now, making poster-scanning or Bluetooth-enabling compulsory is not on the table.
How good is Bluetooth tracing?
There's no satisfactory answer to this question.
Whereas NZ resisted Bluetooth tracing with the first few versions of the NZ Covid Tracer app, Singapore and Australia jumped in boots and all, but suffered from glitchy data due to the fact there are different standards and strengths of Bluetooth on different phones, and not everyone turns the feature on.
The Apple/Google Exposure Notification Framework sought to solve a lot of these problems by working under the bonnet and always being on - something the pair can achieve because between Apple's iPhone and Google's Android software, they run almost every phone on the planet.
But the final version of their most recent spec was ready only weeks before NZ adopted it. It's so far been used mainly by a handful of small countries where Covid is largely under control, plus a few states in the US where the virus is wildly out of control, making contact-tracing efforts of all kinds futile.
Not everyone's a Bluetooth booster.
AUT business information systems lecturer Dr Farkhondeh Hassandoust warns: "Despite the benefits of Bluetooth technology in the NZ Covid Tracer app, there are some potential issues with this functionality.
"For example, environmental factors may affect the accuracy of Bluetooth. Bluetooth signals may collide with walls and be absorbed by our clothes. These factors could potentially confuse the contact tracing capabilities, making a Bluetooth device that is 2m away appear to another device as if it is 10m away and vice versa. Therefore, there are risks of the upgraded app showing false positives and false negatives."
Otago University public health professor Nick Wilson says because of those kinds of practical drawbacks with smartphone-based Bluetooth tracking, it is important the Government pursues other measures too, including data from phone networks, plus token or card-based Bluetooth tracking - such as the Covid Card pilot in Rotorua.
Regardless, Bluetooth tracing is another tool in the Ministry of Health's toolbox - and it will need as many as it can if - or rather when - more community transmission occurs.
"In the event of there being Covid-19 cases in the community, Bluetooth tracing might help notify people who have been exposed to Covid-19 more quickly so they can take action faster," Chen says.
"If we can get people who may have the disease to isolate and get tested faster, then we can cut off the chains of transmission and reduce the spread of the disease."
Will Big Brother be watching me?
Privacy Commissioner John Edwards - often times a strident critic of Big Tech - has given the Apple/Google Exposure Notification Framework, as used for the NZ Covid Tracer App's new Bluetooth tracking feature - his seal of approval.
"No personal information is shared with Apple or Google," Edwards says.
The privacy safeguards in the app's Bluetooth tracing function means a phone keeps a coded record of other phones with the app which come near it, but it does not collect any identifying information. This information remains on a user's phone for 14 days only, and is not disclosed to the Ministry of Health unless a user gives their permission, Edwards points out.
A squad of academics say the Privacy Commissioner is right. AUT computer science professor Dave Parry, for example, says: "Apple and Google have developed a robust, secure and privacy-preserving system and it's good to see the NZ Government adopting this. There is no real risk to privacy, at each stage you have to choose to release your data and all the tracing centre knows is the original person who tests positive - which they know anyway."
Auckland University's Dr Andrew Chen notes the Bluetooth-tracing system includes several privacy safeguards that anonymise data. It gives each phone an ID number for each day, for example.
If someone gets infected, then their phone's ID number will be placed on a Ministry of Health online register, which every NZ Covid Tracer users' phone will check several times a day.
If the app discovers you've been in contact with an infected person, you'll get an alert - which could differ depending on circumstances. A glancing contact could generate a message saying you should call health authorities, for example, while an hours-long contact would result in an alert to seek a test immediately.
That's how it works on paper. How it works in reality is yet to be tested, given NZ's lack of community transmission since Bluetooth was enabled. But we do know that the more people who enable the feature, the better the results are likely to be.