In a statement issued by the Ministry of Health this afternoon, it said the DHB rang 50 people yesterday to apologise and inform them of the actions now being taken.
"The key concern of many of those contacted was that their booked vaccinations would go ahead as planned - which they will. This process of contacting individuals continues today. Where individuals are unable to be contacted by phone, the DHB will be making contact through email."
The DHB said a "relatively small number" of people were "understandably upset".
"Again, the DHB has apologised and has also explained that the appointment system remains offline until the issue is rectified and the system thoroughly tested.
"At this stage, the external booking issue is limited to Canterbury DHB and to household members of frontline border workers at that DHB who had been invited to make appointments to be vaccinated."
The Ministry of Health said Hutt Valley and Capital & Coast DHBs were using a different version of the booking system used in Canterbury, but access is password protected and only available to DHB staff on their internal network.
"These two DHBs are reviewing the security of their internal system in light of the issues identified at Canterbury. The DHBs were not planning to use the public facing website that has caused the issue in Canterbury.
"No other DHBs are using the system for making Covid-19 vaccination appointments.
"A national booking system, using different software to Canterbury's interim booking system, and using a different IT approach, is currently being developed by the Ministry of Health to support scaling of the vaccine programme."
The Ministry said there was no evidence of any malicious breach, access to this information or sharing of it further.
There are no new community cases of Covid-19 and just one new imported case reported today, the Ministry of Health said.
The new case was a person who arrived from ireland via Qatar on March 18 and tested positive on day eight.
There are 75 active cases and there has been a total of 2126 cases in New Zealand.
The Ministry said the investigation into the 'day 12' case at the Grand Mercure managed isolation facility in Auckland was continuing.
"As at 9am this morning, a total of 235 of the 258 returnees have now been contacted and 167 have returned negative test results so far."
Yesterday, the Health Ministry reported one new case of Covid-19 in managed isolation and one historical case.
