The Health Ministry is looking into it, he said.
Just over 705,000 New Zealanders had received a first dose and more than 440,000 had received a second dose by yesterday.
In group 3, 206,406 have had a first dose, and 91,477 have had a second dose.
On Tuesday, Hipkins warned that vaccine stocks will be at "almost zero" by next Tuesday, before the country receives another shipment.
As a result, the Government is banking on another shipment of 150,000 doses arriving next week to avoid running dry.
It has also announced that all up, the country is due to receive one million doses from Pfizer this month.