Thirty-nine of the new cases are in the community and 10 are in MIQ. There are four new border cases of Omicron, bringing the total in New Zealand to eight.
The Ministry of Health said none of the eight cases had been in the community.
Of the 39 new community cases, 25 are in Auckland, 11 are in the Bay of Plenty, two are in Lakes and one is in Taranaki.
Forty-nine infected people remain in hospital, including five in ICU.
Of the patients at Northern region hospitals, 24 (59 percent) were unvaccinated or not eligible, six (15 percent) were partially immunised and nine (22 percent) were fully vaccinated. The vaccination status of the remaining two (5 percent) was unknown.
Omicron, the latest variant of concern, is believed to be more infectious than the Delta strain of Covid-19 and is sweeping through the United Kingdom and other countries.
New Zealand's first case was discovered in a returnee in MIQ in Christchurch and a further three cases were detected yesterday in Rotorua.
Two of today's Omicron cases arrived from Singapore on separate flights - one travelled on a flight to Auckland on December 13 and the second case was on a flight to Christchurch on December 15.
Of the eight Omicron cases, two were in a bubble but the other six cases were unrelated to each other, suggesting no cross-contamination or cross-infection either in-flight or within MIQ facilities, the ministry said.
"We are carrying out whole genome sequencing on all new border cases of Covid-19 to rapidly identify any new cases of the Omicron variant," the Ministry of Health said.
All passengers on flights with Omicron cases were required to complete ten days at a managed isolation facility – rather than spending the last three days at home, the ministry said.
"Our health and MIQ teams around the country have been planning for Omicron cases at the border and will continue to manage all arrivals cautiously."
