She said an elimination strategy was the best way to keep Covid-19 out and the economy open.
The prime minister also said New Zealand would move to a new individual risk-based model for quarantine-free travel from the start of next year.
She stressed the priority was vaccinating the population by end 2021.
New Zealand is seen as one of the most successful countries in the world in controlling the coronavirus pandemic.
The country has recorded just 26 deaths in a population of just under five million people.
“We’re simply not in a position to a fully reopen just yet,” Ms Ardern said in a speech at a forum about reconnecting New Zealanders to the world.
“When we move we will be careful and deliberate, because we want to move with confidence and with as much certainty as possible.”
She added that when the country does reopen next year, vaccinated travellers from low-risk countries will be able to visit without quarantining, while those from higher risk countries will have to either self-isolate or quarantine for 14 days.
New Zealand has contained Covid-19 outbreaks and Ms Ardern has won praise for her handling of the pandemic.
Strict border controls and snap lockdowns are among the measures that have kept infection rates low. (BBC News)