It now uses the Bluetooth-based Google/Apple exposure notification (GAEN) framework. This allows Android and Apple (iOS) devices to communicate via a contact-tracing mechanism built into the devices' operating systems.
Meanwhile, Australia continues to use the COVIDSafe app, which also uses Bluetooth, but with a different underlying system.
Quarantine-free travel is allowed from New Zealand to certain safe travel zones in Australia, as long as travellers haven't visited a New Zealand COVID hotspot in the preceding fortnight.
But in this context, New Zealand's COVID Tracer upgrade is unlikely to help as both countries are using different contact tracing systems that can't communicate.
Comparing COVID Tracer and COVIDSafe
While COVIDSafe and COVID Tracer both use Bluetooth to determine proximity between users, and log close contacts with "digital handshakes", both apps have different approaches to reporting close contact information to authorities.
If a COVID Tracer user tests positive for COVID-19, they can alert close contacts who also have the app. These contacts then receive a notification and are advised to self isolate.
New Zealand health authorities can't know the contacts' details at any point unless they themselves come forward.
On the other hand, if a COVIDSafe user tests positive, they can choose to send information about their close contacts directly to Australian health authorities - who can then follow up with manual contact tracing.
Will the apps help form a travel bubble?
Both COVIDSafe and COVID Tracer use different underlying systems and therefore can't work together. This means Australians visiting New Zealand would have to download the COVID Tracer app and use it throughout their visit.
Similarly, a New Zealand resident visiting Australia would need to download and use COVIDSafe. But this may not be possible for many, as setting up COVIDSafe requires a verified Australian phone number and postcode.
And even if travellers do use the other country's app during their visit, this alone won't mitigate the risk of bringing home the coronavirus.
For instance, if they contract the virus shortly before returning home (from someone who didn't know they were infectious) and then delete the app as soon as they return, the news of potential infection won't reach them.
While the update was needed, critics pointed out adopting the GAEN framework would have been a better option, as it's more reliable and lays a foundation for cross-border contact tracing.
It's also relatively straightforward to redevelop existing apps to integrate it within them.
But even if COVIDSafe were redeveloped to adopt this framework, developers would still need to put in time before both COVIDSafe and COVID Trace could work together.
Such a cohesive cross-border contact-tracing solution would also require agreement by both countries on several fronts, including policies governing the technology, data access permission and the location of physical data servers.
That said, this isn't impossible.
Australia and New Zealand could choose to follow the European Union's efforts. Several EU member states, including Germany, Italy and Ireland, have adopted an EU-established service called the "gateway".
The gateway acts as a middle man which relays information between different EU countries' contact-tracing apps. Contact tracing can still occur while a person is travelling between the various countries, as long as their home country's app has adopted the gateway system.
Where to from here?
Using mobile-based technologies for contact tracing comes with a range of challenges. Besides the issues discussed above, it's also crucial for contact-tracing systems to be widely adopted by the communities they're meant to service.
This has proven challenging. Uptake of COVID-19 contact-tracing apps remains low globally, despite governments pushing for mass use.
Meanwhile, Bluetooth itself is fallible. Determining distance between two devices using Bluetooth has limitations, since signal strength (and therefore accuracy) can be impacted by environmental factors.
For example, the signal may be weaker if a phone is kept inside a thick pocket. Or the app may pick up a signal from someone on the other side of a wall, with whom the user never came into contact.
There's probably no quick fix. But if more time and effort are invested, we may discover a more suitable technology that can provide secure cross-border contact tracing, which also doesn't impinge on users' privacy.
Mahmoud Elkhodr is a lecturer in information and communication technologies at CQUniversity Australia