The 90% Project: Positive cases and hospitalisations largely unvaccinated, Ministry of Health data shows

Only one fully immunised person has needed hospital care after contracting Covid 19 during the country's current outbreak - a figure which shows the vaccine is working, according to experts.

Ministry of Health data shows, as at 9am on Monday, only 37 of the 1177 Covid cases recorded in the community had been fully vaccinated two weeks or more before testing positive and only one of those people needed hospital care.

Another 17 people had received both doses of the Pfizer vaccine during the two weeks prior to testing positive meaning the vaccine would not yet have been fully effective. Of that group, there was also only one person hospitalised.

That is in stark contrast to the 93 hospital admissions for Covid patients who had not been vaccinated and 17 hospitalisations among those who had received only one dose.

Vaccinologist Helen Petousis-Harris said the figures were as expected.

"Very clearly the vaccine is showing itself to be highly effective at keeping people safe from Covid. You expect that there's going to be some cases in the fully vaccinated that become very unwell but it's by far and away the minority and this data absolutely supports that."

Of the 1177 Covid cases reported since August 17, 974 people (83 per cent) had not been vaccinated at all when they caught the virus, 260 of those people were under 12 years old and not eligible for the jab.

The other 149 people (12.6 per cent) had received one dose when they tested positive.

Petousis-Harris said the data reflected what was being seen in other countries around the world where the vast majority of hospitalisations for Covid 19 were among the unvaccinated.

"It's always good to have that homegrown experience. We're not different to anywhere else and it is working beautifully here too," she said.

"It's really helpful to somehow remind us and keep that momentum going. This is our way out. I'm not seeing another way out, to be honest."

Medical adviser for the Immunisation Advisory Centre and Otago University Professor Peter McIntyre agreed the data showed the vaccine was working very well.

However, he cautioned a more detailed analysis of the figures was needed to determine the true impact given the huge difference in vaccination rates among age groups and the rapid rollout and uptake of the vaccine in the last seven weeks.

Despite that, he said the Ministry of Health data made it clear the vaccines were working well.

"If we looked at it in more detail we'd almost certainly find that the vaccines were doing even better than this. As a kind of minimum, we can say that you're three times as likely to be unvaccinated if you're a case and four times as likely to be unvaccinated if you're in hospital [compared with the national average of 22 per cent of the eligible population unvaccinated]."

McIntyre said the vaccine had undoubtedly contributed to fewer deaths and hospitalisations this time around.

That was in large part because the vaccine uptake among those over 65 was high with about 80 per cent fully vaccinated and more than 90 per cent having received one dose, he said.

"The message has got through to that older age group who are at risk. If that hadn't been the case and the same thing had happened with Delta in an unvaccinated population in Auckland, we'd be seeing a lot more deaths and hospitalisations because that older age group would be filling up the hospitals."

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McIntyre said the difference with Delta was that it was much more infectious and more dangerous to the unvaccinated.

"On a case by case basis, your chances of ending up in ICU or hospital with Delta if you're unvaccinated are greater than they were back in 2020. But on the upside, it doesn't look like the vaccine's performing any less well against Delta."

That meant, it was very unlikely the vaccinated population would get severely sick even if they did contract the virus, he said.

"That's good news and it's also an incentive for the unvaccinated to say, 'hello, the benefits to me of being vaccinated have just gone up a lot because if I stay unvaccinated and Delta comes, which it will eventually, I'm in the firing line," McIntyre said.

"The cut-through is things are looking even worse for you if you're unvaccinated with Delta.

"Even if you're young and healthy, sure it's still unlikely that you'll have a major problem, but the chances of that have gone up quite a bit. So don't kid yourself that you're going to be fine if you just keep going to the gym and having a macrobiotic diet. It's not going to do it for you."

Looking to the future, Petousis-Harris said the number of cases among the vaccinated population could start to increase because the majority of the population was in that category, however, by percentage that number would remain small.

The need for booster shots was also likely to become more obvious with an increase in serious cases among the fully vaccinated elderly and high-risk populations, she said.

"There's no evidence that the vaccine isn't holding up well against Delta but what we're seeing is a waning of protection in the people vaccinated earlier and in the older age groups."

As with other vaccines, a booster shot would elicit a far greater immune response than the first doses which would give broader protection that lasted longer, she said.