Northland has been singled out as the worst performing district health board (DHB) when it comes to the Covid-19 vaccine roll-out, falling short of its target by almost 4000 doses.
The latest figures, published by the Ministry of Health, put the nationwide programme slightly ahead of schedule, but there is massive variance between regions.
As of Sunday night, Northland DHB had administered just 6252 jabs, or 62 percent of its target.
Lakes DHB, based in Rotorua, also missed its goal delivering just 76 percent of the vaccines it was supposed to.
In contrast, Whanganui, Nelson Marlborough, MidCentral, Bay of Plenty and Hawke's Bay DHBs all exceeded at least 130 percent of their targets.
Director-General of Health Ashley Bloomfield said his officials had raised Northland's poor performance with the DHB last week.
"We would always expect some DHBs to be a little behind," Dr Bloomfield said.
"Most of them are ahead of what their plans were.
"We follow up with [the ones that are behind] to find out what might be the reasons behind it and what they're doing to catch up."
On Tuesday, Northland DHB expanded its eligibility criteria for the jab, lowering the age limit from 65 years to 50.
"There was a big effort to make sure that the vaccines that were available there were being used," Bloomfield said.
As of yesterday, more than 232,000 doses of the Pfizer vaccine had been administered country-wide, reaching about 103 percent of the national plan. About 60,000 people had received both doses, meaning they were now fully vaccinated.
Associate Health Minister Ayesha Verrall told reporters DHBs were collectively on track to deliver more than one million doses by the end of June.
"We are progressing well against the plan which will see us steadily and then significantly ramp up the rate of vaccination as the year goes on."
Dr Verrall warned New Zealanders to expect "real challenges" over the coming months.
"Rolling out a vaccination programme of this magnitude is an enormous undertaking and it's complex," she said.
"It's important to remember that we will have enough vaccine for everyone. To achieve our aim of having everyone vaccinated by the end of the year, we do need New Zealanders to work with us, and in some cases to be patient."