Northland Māori health provider Ngāti Hine Trust chief executive Geoff Milner said it was "highly unlikely" they would be ready to vaccinate children on Monday.
"Many Māori health providers and vaccinators in Northland don't start up fully until the 24th of this month. So, progressively from the 17th and then the 24th at capacity.
"So I think the stated goal of vaccinations taking place on Monday the 17th; I think there's a bit of time for that to become a reality."
Milner said the week-long gap between children becoming eligible to be vaccinated before services could deliver would likely bear out nationwide.
RNZ has spoken to a number of health providers, both Māori and non-Māori, which also said the were ramping back up to full capacity from 17 to 24 January.
Milner's advice for parents who may have to wait a little longer to get their tamariki vaccinated was to make use of the delay by informing themselves and their children.
"Vaccinating children is a delicate and very emotive issue so for parents; take that time to have conversations with their children and do some further research around the Medsafe accreditation of the Pfizer vaccine.
"Once the system gets up and running there will be no shortage of vaccination capacity; parents will be able to get their children vaccinated."
There are 476,000 children between ages 5 and 11 who will become eligible for their first dose of the Pfizer vaccine on Monday.
The vaccine will not be mandatory and they will not need vaccine passes.
