New Zealand's first case of the Omicron variant of Covid-19 had arrived in the country from Germany, via Dubai and Auckland, last Friday.

The case has prompted experts to urge the Government to delay opening the border, restrict passengers from high-risk countries, and reconsider allowing Covid-19 patients to isolate at home.

Director-General of Health Dr Ashley Bloomfield confirmed on Thursday the positive case was now in the Sudima managed isolation and quarantine (MIQ) facility in Christchurch. All passengers on the person's flight to New Zealand, which came from Germany via Dubai and Auckland on Friday, had been deemed close contacts and were staying on the same floor as each other.

Bloomfield said the risk to them was deemed low, as protocols included that people could not leave their rooms until day-one test results were returned.

The person with the Omicron variant, who was double vaccinated and usually lived in Germany, had been moved to a specialised quarantine facility. It was not known if they were a New Zealand citizen.

Bloomfield did not rule out further lockdowns should Omicron spread to the community. “We would just have to see what the situation was.”

Government ministers would meet on Friday to consider whether New Zealand’s vaccine booster programme should be accelerated – something that had happened in several other countries already, he said. Boosters were currently recommended in New Zealand six months after a second vaccination.

Sudima Hotels chief operating officer Les Morgan said nothing would need to change with the arrival of the Omicron case.

“The hotel has a quarantine wing. Hotel staff themselves have no contact with the people in there – that's all done by the health services. It is a reasonably strict facility already.”

The World Health Organisation​ (WHO) has warned Omicron is spreading at an “unprecedented rate” after being reported in 77 countries, and is likely to outpace the Delta variant. Britain recorded nearly 79,000 new Covid-19 infections in a single day.

The Omicron variant appears to cause less severe disease than previous versions of coronavirus. The Pfizer vaccine seems to offer less defence against infection but does offer good protection from hospitalisation, according to an analysis of data from South Africa.

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While the findings are preliminary and have not been peer-reviewed, they line up with other early data about Omicron's behaviour, including that it seems to be more easily transmitted.

Those returning from other countries would be able to do the same from February 14, while the border would begin to open to all fully vaccinated arrivals – not just citizens or residents – from April 30.

Public health expert Michael Baker said the Government had to decide if it wanted to keep Omicron out or if it wanted to live with the new Covid-19 strain.

He believed New Zealand needed to take a cautious approach and try to keep Omicron out until more was known about it.

Baker also wanted the Government to delay opening the border to Australians on January 17 by at least a month. He called for a complete review of MIQ and wanted the Ministry of Health to promote booster vaccines, which he believed should be issued five months after the second vaccination.

On Monday, Prime Minister Jacinda Ardern indicated the start date for letting returnees skip MIQ may be in jeopardy because of Omicron.

Fully vaccinated New Zealand citizens and residents returning from Australia are supposed to be able to bypass MIQ and self-isolate for seven days starting from January 17, the Government announced last month.

However, Bloomfield said he was not reconsidering self-isolation at home, as early evidence suggested Omicron’s incubation period was shorter than Delta, giving confidence that cases would be picked up within the seven-day MIQ period.

The University of Auckland’s Dr David Welch, a senior lecturer from the Centre of Computational Evolution, said Omicron was the “fastest spreading variant we have seen”.

Cases in South Africa, Australia, the UK and Denmark had shown the doubling time for daily cases was about two to three days, meaning 10 daily cases could become 10,000 daily cases in less than a month, he said.

“Like all other variants, we can expect Omicron to arrive in Aotearoa, and we need to quickly prepare for it.”

The variant had to be kept out of the country while we got prepared, he said.

“Keeping it out requires ongoing maintenance of the MIQ system for all arrivals into the country, whether vaccinated or not.

With rapid spread in Australia, the plan to allow NZ citizens to return with no MIQ from 15 January should be immediately postponed.”

Welch believed the vaccination requirement for arrivals should also be raised to three doses and said high levels of testing in the community needed to continue.

“The traffic light system will likely need strengthening if an Omicron outbreak occurs before the population is more widely vaccinated,” he said.

“The testing and tracing systems also need to be boosted to prepare for a large outbreak.”

University of Otago professor of public health Nick Wilson said he did not expect Omicron to arrive in the country so soon as New Zealand did not have that many Covid cases in MIQ.

Experts were still at an “early stage” in their understanding of the Covid-19 variant.

“This Omicron looks like it's more transmissible, but it may be less severe.

“If it’s more vaccine-resistant that is a concern because ultimately it may infect more people ... But if it does spread widely in New Zealand it will basically immunise the unvaccinated population because they'll get infected.”

Associate Professor Siouxsie Wiles, of the University of Auckland's School of Medical Sciences, said people who’d had two doses of the vaccine were not as well protected against Omicron as they were against Delta.

“Decisions will be made about whether our booster programme should be brought forward, earlier than six months.”

ESR principal scientist Professor Mike Bunce said it was “only a matter of time” before Omicron presented at the border.

“The hope is that it stays at the border.”