Covid-19: How does vaccination affect the chances of hospitalisation with the Omicron variant in New Zealand? – Stuff.co.nz

Kiwis who remain unvaccinated are about 12 times more likely to go to hospital with Omicron than people with two or more vaccine doses, new data suggests.

And they are 27 times more likely to end up in hospital compared with those who have had a third booster shot.

The data also comes with a warning for the 1.44 million New Zealanders overdue for a booster shot: overseas research suggests their protection against symptomatic Omicron infection has waned to about 30 per cent effectiveness.

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Stuff has collated new cases and hospitalisations detected since late January to create a dataset made up predominantly of Omicron cases. As the outbreak grows, the data suggests who is more likely to experience severe outcomes.

Omicron is a less severe disease than either the Delta or original variants of Covid but can still result in hospitalisation or death.

Since January 27, there have been just under 5900 cases of Covid-19 detected in the 12+ population and 41 have so far needed hospital care.

While unvaccinated people only account for four per cent of those cases so far, they account for 34 per cent of hospitalisations.

For every 100,000 unvaccinated people, 5.3 have gone to hospital with Covid, compared to just 0.5 for every 100,000 double-dosed people.

The difference is even starker compared to those whove had a third vaccine dose.

The Health Ministry told Stuff fewer than five of those hospitalised with Covid had received a booster shot. It would not confirm the exact number, citing privacy reasons while case numbers were low.

Assuming the upper limit of four cases, the hospitalisation rate among the boosted population (1,959,875) is just 0.0002 per cent at the most two in a million.

Among diagnosed cases, the rate of hospitalisation treatment is again much higher for the unvaccinated. About 6.7 per cent of unvaccinated cases have needed hospital treatment compared to 0.5 per cent of people who are at least double-dosed.

Melbourne University epidemiologist Tony Blakely says the rates are naive rates they do not take into account age or the length of time since someone last had a dose of vaccine, which wanes over time.

But despite that morasse of possible combinations, the overall picture the data paints is in line with what has been observed elsewhere.

We know enough from other countries, including Australia, that the vaccine works, Blakely says.

Your chance of being hospitalised and even more so your chance of ending up in ICU, and even more so than that, your chance of dying, is much less if youre triple-vaccinated, recently, than if youre unvaccinated. The difference there is 35 to 50-fold in risk.

Someone who was unvaccinated was 34 times more likely to need ICU care than someone with three vaccine doses.

Stuffs data also revealed a more surprising statistic: the overall case rate for those who are at least double-dosed is now higher than for unvaccinated people.

For every 10,000 unvaccinated people, 7.9 have been diagnosed with Covid since late January. The rate for people with two or more doses is 11.7 cases per 10,000 population.

But there are multiple caveats on this data which mean it cannot be taken as an indication of the vaccine's effectiveness at preventing infection with Covid-19.

Many of the people still out and about under New Zealands red light control settings are younger age groups, who are less likely to be boosted yet and so will have rapidly waning immunity, Blakely says.

If youre only double-vaccinated the vaccines effectiveness [against symptomatic infection and hospitalisation] is about 70 per cent but it goes down quickly.

UK experts have also suggested vaccinated people may be more likely to get tested and that fully inoculated individuals behave differently for example they have greater access to cafes, bars and other close-contact settings.

Data from the most recent UK Health Security Agency Covid-19 monitoring report suggests that by 10 to 14 weeks after a second dose, the Pfizer vaccine only has about 30 per cent effectiveness against symptomatic Omicron infection, and 50 per cent effectiveness against hospitalisation (the effectiveness is better for Delta).

A booster raises effectiveness back up to about 70 per cent against symptomatic infection and 90 per cent against hospitalisation.

MARTIN DE RUYTER/STUFF

Wendy Low gives a booster vaccine to a person in Nelson.

Data from the Health Ministry does not split overall case numbers into those who have had only two doses and those who have had a booster, meaning there are no separate case rates for the boosted population.

[If] you only see two-plus doses in the data (not double separated from triple), then you will observe what you observe, Blakely says.

New Zealanders yet to receive their booster are not too late, he says.

Given youre still at the bottom of the [Omicron] mountain, theres still plenty of time. The more people that get boosted, the fewer people who go to hospital.

It was important to remember the risk of severe disease from Omicron is still low for young, fit and healthy people, Blakely says.

So the important focus for New Zealand as Omicron washes through society is that you protect the older people in society massively. You help them to hunker down.

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Covid-19: How does vaccination affect the chances of hospitalisation with the Omicron variant in New Zealand? - Stuff.co.nz