The latest data on cases and hospitalisations in the Delta outbreak shows how vaccination status is a deciding factor in whether people are infected or become severely ill, Marc Daalder reports

Unvaccinated New Zealanders are disproportionately represented among new Covid-19 cases and hospitalisations in the community outbreak, in a pattern that mirrors trends overseas.

More than 82 percent of the Delta cases found as of Monday have been unvaccinated. An even higher proportion of those in hospital were unvaccinated.

That’s close to double the 42.8 percent of the general population that isn’t vaccinated. Receiving both doses of the vaccine is more effective as well, with just one fully vaccinated person ending up in hospital, alongside 15 people who had received one shot.

Almost 30 percent of the population has been fully vaccinated and 28 percent have had one dose.

On these numbers, an unvaccinated person is 119 times more likely to end up in hospital than a fully vaccinated person and eight times more likely than someone who had received one shot.

But these numbers might not be telling the fully story. Vaccinologist Helen Petousis-Harris says it can take a couple of weeks after the vaccine is administered to reach full efficacy.

"You've got to allow time for that injection to take effect. It's not instantaneous as soon as it's administered, it takes a period of time for the body to have that immune response," she said.

"Two weeks after the second dose, you start hitting a peak antibody response."

On that basis, a full 95.9 percent of those in hospital had been unvaccinated two weeks prior to testing positive. Just four had received a single shot at least two weeks before they were tested and none were fully vaccinated.

For cases, nearly nine in 10 were unvaccinated two weeks before they returned a positive test result. Just over 7 percent had received one shot and the remaining 3 percent had received two shots at least a fortnight prior to testing positive.

This echoes a pattern overseas, where many countries with 50 to 60 percent of their populations vaccinated are experiencing new waves that have been dubbed the "pandemic of the unvaccinated".

"You can look at just about any graphs overseas and you see that resurgence. But when you plot vaccinated and unvaccinated, vaccinated are just a flat line along the bottom," Petousis-Harris said.

"It's overwhelmingly in this unvaccinated population. So you do seem to have these two different populations."

Hospitalisation data from Seattle shows the "pandemic of the unvaccinated" in effect.

In light of the data from New Zealand and overseas, the Government has redoubled its efforts to get people vaccinated.

"The important point I would make is that when you look around the world, the thing that’s determining whether or not you’re seeing that high rate of hospitalisations - and, very sadly, loss of life - is vaccination rates," Jacinda Ardern said.

"It is the greatest tool we have been given in the Covid battle to date, and we must use it.

"We’ve got very good data even from just this outbreak in New Zealand showing that the risk of both becoming a case and certainly of being hospitalised is much, much lower if you’re fully vaccinated, and is lower even just with a single vaccination," Director-General of Health Ashley Bloomfield said.

"So it is real-world, real New Zealand evidence that being vaccinated protects you and your family and the wider community from Covid-19."

Petousis-Harris' final takeaway?

"The vaccines are working very well and this is consistent with what we've seen overseas. Get vaccinated."

Marc Daalder is a senior political reporter based in Wellington who covers climate change, health, energy and violent extremism. Twitter/Bluesky: @marcdaalder

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