An MIQ cleaner is believed to have caught Covid-19 from an infected traveller, but Covid-19 Response Minister Chris Hipkins has no concerns about the processes in place to prevent such infections.
The cleaner had also received two doses of the Pfizer vaccine, but it takes two weeks after the second dose for the vaccine to become fully effective - and it's not 100 per cent effective.
The worker and their family are in self-isolation, and while three family members have tested negative, one has returned a weak positive result and was being retested immediately.
Only two other contacts, both work colleagues, and one location of interest - the Mt Roskill Countdown on Stoddard Rd - have been identified so far, but that circle could widen if the positive result of the family member is confirmed.
Anyone at the supermarket on Saturday between 3pm and 3.15pm is regarded as a casual contact and are asked to monitor their health until April 3.
Hipkins said there was no reason to change alert levels at this stage because the risk was low and there was no evidence of potential transmission in the community.
Genomic sequencing is expected to confirm that the cleaner caught the virus from one of eight Covid-positive travellers who stayed at the Grand Millenium this month, but it remains unclear how the cleaner got infected.
Infection prevention protocols at the Grand Millenium were last reviewed in January, and Hipkins said there were only "mild to moderate recommendations for improvement".
"There was nothing in that review that rang any alarm bells ... We haven't got concerns around the way [the Grand Millenium] operates."
That was despite two complaints in January about staff in close proximity to other people, which Hipkins described as "low-risk breaches I'm not particularly concerned about".
Masks were worn in both incidents, he said, and there was no physical contact in the second case.
Auckland University aerosol chemist Dr Joel Rindelaub questioned whether there should be a stand-down period for rooms when vacated by a traveller.
"Since the virus is not expected to 'live' in aerosol particles for more than three hours or on surfaces for more than three days, having a delay prior to accessing a vacated room could allow the virus to degrade naturally before any possible exposure to MIQ staff."
Ventilation at the Grand Millenium was being reviewed, but the Ministry of Health said no information can be released as the review is ongoing.
Hipkins also confirmed that an MIQ traveller was told of a positive test result on Sunday while they were exercising away from their hotel - the Grand Mercure in Auckland.
They were then taken back in the same bus as 23 other MIQ travellers who had been exercising, but Hipkins said he wasn't concerned because masks were worn and they were kept physically distant.
Asked if the Covid-positive person should have been transported separately, Hipkins said: "That's one of the things we'll look at."
The 23 MIQ guests are now being retested and have had their MIQ stay extended by five days as a precaution.
The Grand Millenium cleaner returned a positive test result last night despite having a second dose of the Pfizer vaccine five days before being tested.
Immunisation Advisory Centre director Nikki Turner said it took two weeks after the second dose to reach maximum protection, which is thought to be between 90 and 97 per cent effective.
"The good news for this person is that they are asymptomatic ... so we are pleased to see that the vaccination is likely to be providing some protection, even at this early stage.
"The majority of individuals fully vaccinated will not get sick and of the small number of people who did, these people did not have serious illness. That is what we seem to be seeing in this case."
Turner said Covid-19 can still spread among vaccinated people, which highlighted the importance of ongoing continued border protection, use of PPE, and good hygiene practices.