There could be 3600 to 8700 Covid-19 cases a month at the peak of an Omicron outbreak in the Bay of Plenty District Health Board region, according to government modelling.
There would be 100 to 275 needing hospital treatment each month, with five to 10 of them needing ICU treatment, the Ministry of Health says.
That was provided the outbreak followed the patterns seen in Australia over summer, and adjusted for the vaccination and booster rates that the Bay is on track to achieve.
Omicron has already arrived in the Bay, with Tauranga's first two cases announced on Tuesday. One other in that pair's household has since tested positive.
As of yesterday, the city had 11 confirmed or suspected Omicron cases. Eight were connected to an exposure event at BestStart in Pyes Pa. A new case of unknown variant was also being investigated. There were 105 cases nationwide.
Polo in the Bay, held at Trustpower Baypark Stadium last Saturday, was named a high-risk exposure event.
People who visited the event's lounge bar between 1pm and 6.15pm and the Good George gin caravan from 2pm to 4.30pm are considered close contacts and must isolate and test. Others in the stadium are casual contacts and should monitor their symptoms.
It comes after New Zealand moved to the red Covid-19 setting on Sunday after the first Omicron community cases were detected. Prime Minister Jacinda Ardern said she expected the country to stay at red for "some weeks".
As of yesterday, 92 per cent of the Bay of Plenty's population aged 12 or older was double vaccinated and 95 per cent had at least one dose.
A Ministry of Health spokesperson said the predictions would have been "almost twice as high without the vaccination and booster rates the Bay is on track to achieve."
"Boosters do make a difference to the number of cases."
"Mask wearing and other social measures will also 'flatten the curve' and could reduce the number of cases even more."
Bay of Plenty DHB Covid-19 incident controller Trevor Richardson said Omicron patients would be managed similarly to other Covid patients the hospital had treated.
The difference with Omicron would be a greater number needing care and potential increases in staff sickness, he said.
A main lesson from overseas was the importance of managing who all who came into the hospital.
"We will always be there for people who are sick and need care but we ask for consideration and respect for the need to do things differently, which might require understanding if things look different or you are sent somewhere or managed in a different manner.
"Consider where more minor problems can be addressed including services such as community pharmacies in addition to the GP or Emergency Department, who will both likely be under significant pressures.
"We need to look after each other in these times and if friends or loved ones are struggling both help and reach out for support to prevent reaching a crisis point."
Richardson said there was a dedicated Covid-19 ward at Tauranga Hospital with ventilation for Covid patients and the board had continued to develop other areas that would provide more beds and better environments across its two emergency departments.
There would also be a "big push" to lift vaccination numbers, particularly for Māori and 5 to 11-year-olds, as well as boosters.
Toi Te Ora Public Health medical officer of health Dr Bruce Duncan said the Bay of Plenty was "well-prepared" for an Omicron outbreak with high vaccination levels, boosters, the child vaccine available and public health measures in place.
"These measures will help slow the initial spread of Omicron. However, it is important to prepare now for an Omicron outbreak in our communities."
Duncan said Toi Te Ora's response plans had been adapted to deal with the Omicron variant.
It was working closely with local partners to plan for a comprehensive public health response to living with Covid, he said.
Te Puna Ora o Mataatua Charitable Trust chief executive Dr Chris Tooley said the most "effective" way to prepare for these numbers was to get vaccinated and get boosters.
The Eastern Bay kaupapa Māori health service's mobile vaccination teams would go "anywhere anytime ... to make it happen," he said.
The trust had self isolation and quarantine kits "ready to go" for when people tested positive for Covid. These included delivering clinical support, hardship support and food packs.
"What we found last time in the first lockdowns [was] that after a while people starting breaking their bubble because they started to need kai.
"Our Whānau Ora teams and our counselling teams will reach out to them as well just to make sure that things are kei te pai from a hauora wellbeing point of view as well and just troubleshoot anything that the whānau needs."
Tooley said there would be "significant portions of workforce isolating at home or working from home" and encouraged businesses to consider splitting up their workforces "right now".
Poutiri Trust general manager Kirsty Maxwell-Crawford said it had been a "busy week" with booster requests and children getting vaccinated.
The Te Puke-based trust, which did Covid-19 testing and vaccinations, had been briefed on predicted case numbers to help it plan.
"We're expecting a busy couple of months and it helps us to try to put as much pre-planning in as we possibly can while at the same time starting to respond to increases in demand."
She said the trust had not seen an uptake in testing "as much as I would have hoped" and reminded people to be vigilant for symptoms.
"We need vaccination rates but we also need consistent testing to be able to identify as quickly as possible when somebody is positive."
The trust was organising its teams into "work bubbles" so it could keep offering services safely if staff were ill, she said.
Chief executive of kaupapa Māori health service Te Manu Toroa Pat Cook said it was communicating with its most vulnerable clients in the hope of getting people "as prepared as possible" for potential positive cases in their household.
Tauranga Chamber of Commerce chief executive Matt Cowley said most businesses had driven high vaccination levels of their workforce and did not want the public healthcare system overrun.
"Businesses hope the Government goes back to the orange status as soon as we know the peak of the Omicron outbreak is not putting pressure on our public healthcare system."
Tauranga City Council commission chairwoman Anne Tolley said a significant Omicron outbreak in the Western Bay predicted by the modelling would put many systems people relied on under pressure, particularly hospital and medical support services.
"We can help to flatten the infection curve though by getting vaccinated and boosted as quickly as possible, wearing masks when we're out in the community particularly in enclosed spaces, following social distancing guidelines; and observing good hand hygiene."