New Zealand will be plunged into the red light setting within a day or two of Omicron community spread being discovered in a bid to prevent a "tidal wave" of infections, the Prime Minister has revealed.
But an expert is calling for the nation to move into the most restrictive traffic light setting immediately, rather than waiting for an inevitable incursion that could infect thousands of people and overwhelm hospitals.
Five people are now believed to have been in the community with the variant, which appears to be more transmissible but less severe than its Delta predecessor.
One is a Palmerston North case who was active in the community this week, and the others are in Auckland.
Concerns about Omicron prompted the Government to halt new MIQ hotel room applications this week.
And yesterday, it was revealed all of New Zealand will move to the red traffic light setting within 24-48 hours of Omicron community transmission being confirmed.
In the red setting, events cannot have more than 100 attendees, and must use vaccine passes.
Most businesses can choose to use vaccine passes or not, but those requiring certificates generally have greater freedoms in red than those not using passes.
Prime Minister Jacinda Ardern said several Omicron cases had recently been contained at the border.
"We are using our tried and true methods of maintaining high levels of testing, contact tracing and isolation to prevent it taking hold in the community," she said yesterday.
"But once Omicron arrives, we will need to step up further."
The PM said reports from overseas showed Omicron cases could grow from the hundreds into the thousands within a fortnight, so families and businesses should prepare.
"Think about what you need at home if you are required to isolate. Think about contingency planning should parts of your workforce need to stay at home."
Ardern said the new variant made an elimination strategy virtually impossible.
The Government said no widespread or regional lockdowns will be imposed when Omicron gets into the community.
But lockdown-type restrictions could be activated in specific workplaces, educational facilities, or rural areas with low vaccination rates.
"I don't think anyone believes that Jacinda Ardern is not going to bring back lockdowns if the hospital system is overwhelmed," Act leader David Seymour said.
"The truth is, if you get a region where the ambulances are lining up at the A & E door and people are in the corridors on stretchers, she will go to lockdowns."
He believed lockdowns would be necessary if the health system faced such severe strain.
But a vaccine booster shot programme now and boosting hospital capacity could help avoid that scenario, Seymour said.
He and National Party leader Chris Luxon accused the Government of having no plan for Omicron.
"New Zealand has been slow on boosters and slow on vaccines for 5–11-year-olds and now we're being appallingly slow on rapid tests," Luxon said.
"Rapid tests will be critical, but the Government doesn't have enough."
Luxon said businesses seeking permission to import rapid tests have had applications languishing in bureaucratic quagmires for weeks.
Dr Jennifer Summers, a University of Otago epidemiologist, said concerning gaps existed in the country's preparation for an Omicron outbreak.
She said moving New Zealand to the red setting only when community cases were confirmed was inadequate, given Omicron's transmissibility and rising cases at the border.
"The Government needs to be proactive right now, rather than waiting for community cases."
Immunologist Dr Dianne Sika-Paotonu said it was crucial to delay an outbreak as long as possible, to avoid hospitals being overwhelmed.
"A maintained focus on vaccination, boosters, border controls and public health measures is still needed. Covid-19 testing efforts must also continue," she added.
Public health scholar Professor Nick Wilson said the Government must reduce the number of people with Omicron entering the country.
"The Government is wise to show concern about the potential threat of an Omicron outbreak and to highlight as it did that we need more time to get booster doses and to vaccinate children, but it's not addressing the key issue, which is the border."
He said international border restrictions were the best way to buy more time.
The new suspected Omicron cases in the community included a person in Palmerston North who previously tested negative five times in MIQ at Christchurch before leaving an isolation facility on Sunday.
The person became symptomatic on Tuesday, but would have been infectious the day before, the Ministry of Health said.
After the positive test result, 15 locations of interest in Palmerston North were identified.
The ministry said the person was fully vaccinated, and isolating at home with family.
In Auckland, all customers who visited Ara-Tai Cafe in Half Moon Bay on Tuesday afternoon were considered close contacts of an Omicron case.
They were asked to isolate immediately and get tested.
Overseas, Omicron has spread rapidly in some countries but much available evidence suggests it is less likely to cause severe illness than Delta.
In Britain, face masks and vaccine passport mandates will be scrapped in many regions after Prime Minister Boris Johnson said the Omicron infection surge had peaked.
Omicron was first detected in November at laboratories in Botswana and South Africa.
A Stellenbosch University study published in the Lancet on Tuesday suggested full vaccination followed by a booster dose offered good protection against severe disease from Omicron.