Covid-19: Delta outbreak hospitalisation rate falling, but who has needed hospital care?
Hannah Martin05:00, Oct 30 2021This is a modal window.
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STUFF
Have you come across some claims on the internet about injuries or deaths from the Covid-19 vaccine?
The proportion of people being hospitalised with Covid-19 in the Delta community outbreak is decreasing overall, despite the number of new cases growing.
To date, 241 people have been hospitalised since the virus re-emerged in the community in Auckland, ballooning into an outbreak with 3000 cases across five regions.
As of Friday, there are 39 people in hospitals with Covid-19 – four in intensive care or high dependency care units – 2.6 per cent of 1485 active cases.
Kelly Hodel/Stuff
The number of active cases in the Delta community outbreak continues to grow, but the proportion of these cases requiring hospital-level care appears to be falling.
A fortnight ago, on October 15, when there were 664 active Covid-19 cases, 34 people were in hospital – 5.1 per cent of all cases.
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Te Pūnaha Matatini Covid-19 modeller Professor Michael Plank said there were likely a number of factors driving this.
Vaccination tends to push cases towards younger age groups, because older groups have higher vaccination coverage – reflected in the fact this has been an outbreak predominantly in younger people.
Younger people tend to have a lower risk of becoming severely ill from Covid-19, meaning the proportion of these cases needing hospitalisation is lower, he said.
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Mathematics Professor and Covid-19 modeller Michael Plank said the fact that older age groups have higher vaccination rates will be pushing infections into younger people, who are at less risk of severe illness than their older counterparts.
This trend was broadly expected: there has been just a small proportion of cases in the over 60s in the outbreak, partly because that age band has the highest vaccination coverage.
Those under 60 have lower coverage, but the level of risk is not the same – those aged 40-60 have a higher risk of severe illness than those aged 20-40, for example.
As with other Covid-19 outcomes, research shows the rates of severe infections (requiring hospitalisation) and critical infections (requiring critical care, or ICU admission) increase exponentially with age.
This is borne out in the hospitalisation rate by age during this outbreak.
For example, data as of Thursday shows the proportion of children aged between 0-9 in hospital was 1.8 per cent. This grew to 6.7 per cent in those aged 20-29; 8.5 per cent in 30-39-year-olds; 14.7 per cent in those aged 40-49, and 15.9 per cent in 50-59-year-olds.
While the number of infected people over the age of 60 was smaller, the proportion of those cases in hospital was greater: 17.4 per cent of those aged 60-69, and 35 per cent of those aged 70+.
Plank said other factors at play could be that health services were getting better at managing cases in the community or in primary care, as opposed to admitting people to hospital.
The fact that the outbreak was spreading more widely geographically could also be contributing to this, he said. The virus may be less concentrated in high-risk groups (such as people with underlying health conditions, or in more deprivation) than it was a few weeks ago.
Plank said they had seen in other countries, and in their modelling, that vaccination weakens the link between cases and hospitalisations. The higher the vaccination rate, the lower the proportion of cases going to hospital.
However, it doesn't sever the link entirely. If you double or quadruple the number of cases, you could still double or quadruple the number of hospitalisations, he said.
The number of people in hospital with Covid-19 peaked over the weekend, with 55 cases requiring hospital-level care on Saturday. This was down to 35 on Monday.
Stuff
Since the Delta outbreak began in August, 42 people have been admitted to ICUs in Auckland with Covid-19.
At the time, the Ministry of Health said this reflected some instances where people were identified as having Covid-19 when presenting for other issues and admitted; or while advice was sought about whether they could be cared for at home or would need to go to MIQ.
A spokesperson has since advised the Ministry does not differentiate between those hospitalised for Covid-19 and those hospitalised for something else who also had Covid-19.
It says there has been no change to the criteria of who is admitted to hospital with Covid-19 or related issues throughout the outbreak – hospitalisations are based on clinical need.
Christel Yardley/Stuff
People aged 40-49 and 50-59 make up the bulk of hospitalisations in the Delta outbreak, despite the majority of cases being in people younger.
Cases aged 40-49 have accounted for the majority of hospitalisations in the outbreak – 53 people or 22 per cent – despite only accounting for 12 per cent (375) of the 3046 total cases.
Those aged 50-59 were the second most hospitalised group – with 47 of the 306 cases in this age group requiring hospital care (20 per cent).
The majority of Delta cases (21 per cent, or 642 cases) are aged 20-29. Those aged 0-9, 10-19 and 30-39 each make up 17 per cent of the wider outbreak.
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Hannah Martin • Auckland health reporter
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As of Friday, 510 children under the age of nine had contracted Covid-19 during the Delta outbreak, but just 10 (4 per cent of all hospitalised cases) required hospitalisation. None have been admitted to ICU.
Two people have died during the outbreak – a man in his 50s and a woman in her 90s.
As well as making up the vast majority of cases in the outbreak (38 per cent to date), Pacific peoples make up more than half of the hospitalisations.
Māori, who make up 1002 cases or 33 per cent of the outbreak overall, account for 27 per cent of hospitalisations, and Pākehā (or Other) make up 17 per cent of hospitalisations, and 20 per cent of the outbreak overall (607 cases).
ALDEN WILLIAMS/Stuff
Just three fully vaccinated people have required hospitalisation for Covid-19 in the Delta outbreak, compared with 178 unvaccinated people.
Forty-two people have been admitted to intensive care units with Covid-19 in the Delta outbreak.
Health authorities were unable to advise how many required ventilators.
The number of fully vaccinated people who have required hospitalisation during this outbreak is incredibly small.
Just three people who have needed hospital treatment for Covid-19 were fully vaccinated at least 14 days before they were reported as a case.
On the other hand, 178 cases requiring hospitalisation had not received a single dose.
There had been 337 cases in people who’d received one dose at least 14 days before being reported as a case – 21 requiring hospitalisation.
An additional 615 cases could not be vaccinated as they were under the age of 12 – 10 of whom required hospital care.
