Around 15 Wellingtonians were given expired doses of the Covid-19 vaccine last week.
Capital and Coast DHB said the doses had expired within the previous 24 hours and were given to a small number of people at a clinic on October 14 and 15.
"This error was picked up quickly as part of regular, existing monitoring processes and the people affected have been contacted," a spokesperson said.
"Fewer than 15 people were affected."
"The incident is being reviewed and it is thought to be an isolated error, but as a precaution, remaining stock is being checked to ensure it is within the expiry date."
At the 1pm press conference, director general of health Ashley Bloomfield said the error included vaccines that were past their 30-day period.
"It had been in the 2-8 degrees special fridge, but it had just passed that 30-day period. Those people have been contacted and encouraged to get a further vaccine."
He said he wasn't worried about it eroding trust in the vaccine roll-out.
"These things affect a small number of people in a programme that's delivered over 6.3 million vaccinations.
"The fact these were found is a reflection of the quality assurance processes that are in place, to make sure if there is anything that could go wrong in the context of tens of thousands of vaccinations delivered each day right around the motu, that actually our systems are there to find them and follow up immediately."