Canberra's health authorities did not know the vaccination status of more than one-quarter of all virus patients admitted to the ACT's public hospital in late January, The Canberra Times revealed on Thursday.

However, Ms Stephen-Smith told the ACT Legislative Assembly health authorities did know the vaccination status of most people but there were glaring gaps at that point due to a change in data collection.

She said the team initially responsible for case management became overwhelmed due to the surge in cases and consequently the responsibility to collect vaccination data moved to the hospitals.

"To put it in summary terms ... the health emergency control centre had previously been responsible for case management information and collected data on all cases of people with COVID-19 and that included collecting their vaccination status," Ms Stephen-Smith said.

"When the number of cases increased very rapidly they were no longer able to undertake that kind of case investigation and there was a switch over to that vaccination status data for people who were in hospital being collected through the hospitals themselves and being reported through the Clinical Health Emergency Coordination Centre through to the health emergency control centre.

"There have also been issues around being able to match that self-reported vaccination status data up with the Australian Immunisation Register data to verify that vaccination status."

The information around the vaccination data was in freedom of information documents released to The Canberra Times.

It showed there had been 393 patients admitted to Canberra public hospitals with COVID-19 since the start of the outbreak, as of January 27.

Health authorities did not know the vaccination status of 109 patients, which represented 27.7 per cent of all people admitted.

The Canberra Times on Monday asked for an explanation as to why health authorities did not know the vaccination status of 27.7 per cent of patients but an ACT Health spokesman mentioned nothing about a change of systems.

Instead, the spokesman said there were a number of reasons vaccination statuses were unknown and these included patients being too ill to confirm whether they were vaccinated and deviations with data held by ACT Health and the Australian Immunisation Register.

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The extensive freedom of information documents also did not include any information around a change of systems.

The documents also showed record-keeping methods failed to properly record the death of one man with COVID-19 in ACT Health's internal systems.

Ms Stephen-Smith also addressed this in question time on Thursday.

"There was a data-matching issue that hadn't been matched and that with the unfortunate sad passing of that individual but through quality assurance processes, of course that was picked up," she said.

"These are complex systems with multiple moving parts and a lot of cases and a lot of individuals, fortunately not a very high number of deaths but each one is very sad and we send our condolences to those families."

It came after The Canberra Times on Wednesday revealed health officials blocked the public release of information around patient comorbidity data, despite knowing it was "an important part of the picture".

Ms Stephen-Smith said these issues were not critical in the context of the public health response.

"Some of these pieces of data are being presented as being fundamentally critical for decision-making in a public health response, but just simply are not fundamentally critical in the context of making decisions about the public health response, so I think there's also that conflation of those issues as well," she said.

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