However, epidemiologist Prof Michael Baker said it was better to have a surplus than not to have enough.
A batch of 539,370 doses of Pfizer vaccines is due to expire on January 31, part of a national available stock of just under 2.7million doses.
Ministry of Health data shows a total of 11,973,297 vaccines have been administered, and 90% of those aged 12+ have completed a primary course.
Of those eligible, 73% of those aged 18+ have received their first booster vaccination.
However, less than half of eligible 50+ year olds have received their second booster, at 47% .
The first booster is available for those aged 16+, and the second is available for those aged 50+, or 40+ for Maori and Pacific people.
Prof Baker said the spectrum of attitudes towards Covid-19 vaccinations ranged from those who were keen to get them as soon as possible to those who opposed them.
However, a large group were "vaccine hesitant".
"There are some people that feel they’ve had two doses of the vaccine and that’s enough, they’re covered — and that’s just not correct."
The effects of a vaccination waned over time, and the coronavirus was able to reinfect people.
These people had not understood the importance of the vaccine, which helped to lessen the impact of Covid-19 infection, including long Covid.
"It’s disappointing that booster uptake isn’t higher."
It was difficult to judge the amount of doses needed in advance, and if there was a surplus, he suggested sending them to countries that did not have any.
Expiry dates also tended to be conservative, and it might be possible to have them extended.
Te Whatu Ora immunisation programme operations manager Rachel Mackay said no further shelf-life extension on the batch set to expire was possible.
"These extensions require submissions by the manufacturer to Medsafe and for these submissions to meet Medsafe requirements."
Ensuring there were enough vaccines available to immunise the eligible population while not wasting them was a balance, and New Zealand was "actively managing its vaccine stocks".
A significant number of people were still eligible to get vaccinations, and she encouraged them to do so in order to have greater protection against becoming seriously unwell.
She did not respond to questioning about whether age limits should be lowered.
University of Otago immunologist and clinical microbiologist Prof James Ussher said age limits were set by experts and should not be lowered simply to use up vaccines.
