Nearly 150,000 unused doses expired at the end of February and have already been destroyed. Another nearly 170,000 doses were unused and due to expire at the end of March and were being destroyed, the Ministry of Health has confirmed.
The wasted vaccines were worth about $8m.
Reti said the number administered was a "terribly small number" and accused Health Minister Andrew Little of being distracted by health sector reforms.
"Measles is more infectious than Covid and is something clinicians like me are dreading rearing its head any time soon. It would be terrible."
Reti said it was another "failure to deliver" from the ministry, which Treasury had recently given a "D" in its investor confidence ratings (ICR) with concerns around project delivery.
Reti questioned Little on the matter in the House on Thursday.
"Because of the pandemic, a decision was made to pause the measles catch-up campaign between March and November 2021 to focus on responding to Covid-19," Little said.
"We have had a health system that has had to respond at pace to a worldwide pandemic and had to go from business as usual to administering currently 10.8 million vaccinations to our population to keep them safe from the horrors of Covid-19.
"That does require trade-offs. The reality is no system, particularly a system of our size, can do absolutely everything asked of it."
Little said the catch-up campaign also came off the back of several warnings about at-risk groups, which the previous National-led government had not heeded.
Vaccinologist Helen Petousis-Harris said she agreed the issue went back years, but to see all of those vaccines wasted was "a terrible thing".
Petousis-Harris said this failed campaign went alongside concerningly-low infant vaccination rates, which had been declining since 2016.
In New Zealand, children are immunised for a range of diseases, including pertussis (whooping cough), pneumococcal disease and measles, between 6 weeks and 4 years old, with further immunisations at 11 or 12 years.
National vaccination rates have fallen in the past few years, with the declines particularly sharp among Māori and Pacific children.
In July last year ministry officials warned the Health Minister in a confidential briefing immunisation rates for Māori children in most district health boards were below the level of 85 per cent required to achieve "herd immunity".
According to the Ministry of Health's latest quarterly figures (December 2021), the percentage of children who were immunised at 8 months of age — a key milestone — was 90.4 per cent of Pākehā (down from 93.9 per cent in the same quarter in 2016); 73.9 per cent of Māori (down from 90.3 per cent); and 85.3 per cent of Pasifika (down from 95.8 per cent).
Most groups had risen from the previous quarter aside from Māori, which dropped another 0.8 per cent.
At 6 months just 52.5 per cent of Māori babies were immunised, compared to 79.1 per cent for Pākehā.
"We are sitting ducks for multiple infectious outbreaks, because we have serious immunity gaps in infants that are unprecedented and declining," Petousis-Harris said.
"And it is our Māori and Pasifika communities who will be most vulnerable.
"Not only will they be at risk but we have built a pool in the community from where infection can spread."
Along with measles, Petousis-Harris said there was also the risk of pertussis (whooping cough) and pneumococcal disease outbreaks, due to those low rates.
"These are tragedies waiting to happen. Those rates have eroded over such a long time and there have been calls for so long for providers to get the support they need.
"It goes right from the ministry to the communities where the work has to happen."
