Professor Michael Baker is warning that every New Zealander will either get Omicron or know someone who gets it.
On Sunday, Prime Minister Jacinda Ardern held an urgent press conference to announce that all of New Zealand will move to red in the traffic light system.
The announcement came after nine COVID-19 cases infected with the Omicron variant were found in the Nelson-Marlborough region. The family had recently travelled to Auckland and it's not yet known how their infections are connected to the border.
The Otago University epidemiologist told Newshub Kiwis have been "very removed from this threat" and he expected to see "tens of thousands of cases" over the next three or four months.
"Nowhere is ever ready because there are degrees of readiness," Baker said. "We will see tens of thousands of cases and unfortunately several hundred deaths in the next three or four months.
"It's the new, new for us. All of us will either get Omicron or know someone that had got it, so we've been very removed from this threat to date, which has been a good thing because now we have a lot more tools to manage it.
"That is helpful but it's still going to be tough and a lot of us are going to get a very unpleasant illness, so we just have to be prepared for that."
Baker said now that Omicron is circulating "rapidly" in the community, the time intervals for the booster and children's vaccine need to be changed.
"Given that Omicron will be circulating quite rapidly, I think we need to review the time intervals for vaccination," Baker told Newshub. "I think we need to shift the timing for the booster down to three months instead of four months to make more New Zealanders eligible because the time for boosters is now.
"It's the same for the children. We can bring down the interval to three weeks which is in the manufacturer's recommendation."
Last week Baker called for the Government to shift to a mitigation plan in his public health expert blog to slow the spread of Omicron once it entered the community.
The Government announced their three-step plan on Sunday to tackle Omicron. Baker supports the system.
"I think it's good. With Omicron, you're moving to a mitigation approach, so you no longer follow elimination or suppression but it's mitigation," Baker said. "Interestingly, the phase we have been in with Omicron has been elimination and stamp it out.
"The first phase of what the Government is talking about is a suppression approach. You're trying to keep cases low and limit the spread and then the last phase is very much mitigation and flatten the curve.
"The middle stage is pretty much a transition stage from one to the other and I do think the Government has framed this correctly. We are still in this stamp it out phase."
