Only 20% of the population in New Zealand is fully inoculated.
New Zealand Prime Minister Jacinda Ardern has extended the country's strict Covid-19 lockdown, saying that "Delta has changed the game".
The government said New Zealand will stay in level 4 lockdown until at least midnight on Friday, while Auckland will spend the rest of the month in lockdown.
"The safest option for all of us right now is to hold the course for longer," Ms Ardern said at a news conference.
"If the world has taught us anything, it is to be cautious with this variant of Covid-19," she added.
The lockdown extension comes after New Zealand recorded 35 new cases in the community on Monday, the largest one-day rise since April of 2020.
There are more than 320 locations of interest linked to the outbreak and 13,000 contacts have been recorded, far more than in previous outbreaks.
In a news conference, Ardern showed a large heatmap of known contacts of existing cases all over the country to justify the decision to extend the lockdown.
Ardern also announced that the country's Parliament sittings would be suspended for a week.
New Zealand has one of the lowest rates of full inoculation against Covid-19 in the developed world, with only about 20% of the population fully inoculated.
