None of the cases in the current Delta outbreak who were fully vaccinated for at least two weeks before testing positive have ended up in hospital.
The Ministry of Health revealed this morning that of the 88 people who have needed hospital care so far, only one them was fully vaccinated and 15 of them had had one dose.
But when a two week gap since receiving a jab was taken into account, none of the fully vaccinated cases and only four people with one dose have been hospitalised.
That means 84 out of the 88 cases in hospital - or 95 per cent - had not had a single dose of the Pfizer vaccine more than two weeks before testing positive.
This follows trends overseas where fully vaccinated people are much less likely to end up in hospital.
Yesterday director general of health Dr Ashley Bloomfield said that care had to be taken with the data, which should be considered in light of when people were vaccinated.
A spokesperson for the Ministry of Health said: "Many of these vaccinations were done just before the cases were detected, so the vaccinations may have happened after exposure to Covid-19."
As of 8am yesterday, there were 855 cases so far in the outbreak: 702 were unvaccinated, 115 had had one dose, and 38 had had two doses.
Vaccinologist Helen Petousis-Harris told the Herald she was pleased to see these results.
"This illustrates that the vaccine works really well, but it's also a reminder that it's not 100 per cent effective, and you don't become bulletproof straight after the first dose."
She said two weeks after one jab, a person is about 77 per cent protected against serious disease from Delta. This jumped to the high 90s two weeks following a second dose.
The vaccine was less effective against milder symptoms, she said: about 50 per cent effective in protecting against such symptoms two weeks after one dose, and 88 per cent effective after the second.
"I'm pleased to see that quite a lot of people in Auckland are getting vaccinated now. It does seem to be keeping people out of hospital."
She said the focus on vaccinating Auckland needed to remain, not only because of the ongoing threat of the outbreak flaring up, but because most of the country's MIQ facilities are based there, making it the most likely place where the virus could leak from MIQ into the community.
Hospitals in Auckland are already stretched with the current outbreak, with dozens of healthcare staff around the country being flown to Auckland to help.
Yesterday there were 37 people in hospital, including eight at North Shore, 14 at Middlemore and 15 at Auckland hospital.
Six patients in total were in ICU or HDU.
Today Prime Minister Jacinda Ardern is expected to announce how many extra doses of Pfizer she has secured to be shipped to New Zealand immediately, and from which countries.
About 550,000 doses have been administered a week for the past fortnight, and the available stock is expected to run dry towards the end of next week if that demand continues.
However, the current demand has slowed slightly, with 72,893 vaccine doses administered of Tuesday, roughly 12,000 fewer than the week prior.