For a start, some people have had trouble getting and using the digital pass. They may have limited access to email or apps. Pharmacies have been assisting such people in person to get print-outs. But tens of thousands have been issued temporary passes.
Then there's the rather haphazard actual use of the passes in places such as cafes, bars, gyms, hairdressers, and cinemas.
Some venues demand sight of a pass at the door to enter; others allow patrons inside and a pass need only be produced if they want to stay and sit down. That gives the virus a chance to spread indoors if someone with it walks in.
Depending on where you go, staff scan the pass, others just look. Some staff don't mention it before they're asked if it's required.
The minimum requirement is a visual check. There is also an official pass verifier app. Venues can choose to ask for ID to check whether the pass is genuine. Some businesses such as gyms have linked the pass to their own apps for members.
Scanning appears to be the bare necessity if this system is to work. People should feel they can rely on it and that people aren't getting through with fake passes, especially to big public events.
Abuse has been hurled at staff in a number of businesses when people have been asked to show a pass, although people have mostly been compliant.
On the other hand, there have been high-profile cases of businesses not using vaccine passes when required or protesting against jab job mandates. There's also been reports of places trying to cater for unvaccinated customers.
These actions go against the purpose of vaccine passes which are meant to provide safety for the vast majority of people who want protection in public while there's an infectious virus in circulation. The passes should also be something of a reward for those people who did the right thing in getting the Pfizer/BioNTech vaccine.
Passes have been used in other countries, such as France and Denmark, to boost vaccination levels during rollouts. That also appears to have happened in New Zealand.
Epidemiologist Professor Michael Baker said: "The new mandates may have turned people to thinking, I want to be fully vaccinated by the time I head off to visit family and friends around the country."
It's hard to see the current pick and mix use of the vaccine passes improving over the holidays.
People's experience of using them in practice is going to depend on where they are in the country and what businesses they interact with.
If people want to be particularly careful they probably shouldn't rely on the passes too much. Instead, mask up when in public indoor places; eat outside when at cafes; observe the social distancing, and hand hygiene rules.
Considering the passes are the public evidence of vaccination status, the certification system should be more straightforward and reliable than it appears to be.
