The Ministry of Health is reporting a growing number of COVID-19 cases at the border, many of which are the highly infectious Omicron variant.
On Sunday, there were 64 COVID-19 infections detected at the border in the previous 48 hours - the majority of which are expected to be Omicron.
The ministry says getting vaccinated remains the best defence against COVID-19, including the Omicron variant.
"We continue to ask everyone who is eligible to get vaccinated, including people who are now eligible for a booster dose," a statement from the ministry said on Sunday.
Siouxsie Wiles, an associate professor from the University of Auckland, echoed that statement on Monday.
"We've done a fantastic job of getting vaccination levels high but with Omicron, because it can infect vaccinated people who haven't had that third dose, we're kind of back where we started again," Dr Wiles told RNZ's Morning Report.
That's why we need to halt Omicron from entering the community for as long as possible to give people time to get the booster, she said.
In the meantime, Dr Wiles told Morning Report New Zealanders should prepare for Omicron.
"What we need to be doing is using every tool in our toolkit… Our masks, our scanning - all of these things need to be completely second-nature to us so that when Omicron does get here, we're ready for it."
Omicron has become the dominant variant in some countries throughout the world including the US, the UK and France.
The variant is more infectious but appears to be less severe than Delta, the World Health Organization (WHO) says. Despite this, they warn that it shouldn't be categorised as "mild".
A "tsunami" of cases could be on the way as global infections soar to records fuelled by both Omicron and Delta, the UN agency has warned.