Confusion and concern over new SA COVID modelling

Doctors are “confused” about conflicting modelling showing the estimated spike in COVID-19 cases and hospitalisation rates once South Australia opens its borders, saying Government-commissioned data released today appears to contradict SA Health estimates presented to them last week.

Nov 01, 2021, updated Nov 01, 2021
Photo: Roy Vandervegt/AAP

Photo: Roy Vandervegt/AAP

The South Australian Salaried Medical Officers Association (SASMOA) is asking SA Health to clarify how many additional acute care and ICU beds will be taken up once the coronavirus delta variant makes its way across the border, following the release of modelling this morning that appears to contradict information the union says was presented to doctors on Wednesday.

According to the SA Health-commissioned University of Adelaide modelling released publicly today, if South Australia reopens its borders while maintaining public health and social distancing restrictions, the median peak ward occupancy would be 36 beds, with an “extremely small chance of demand exceeding 200 ward beds”.

Peak ICU Occupancy is estimated at a median of nine beds with an extremely small chance of demand exceeding 30, while the median prediction for total deaths is 13 over 300 days, with a total range between four and 51.

But SASMOA says Central Adelaide Local Health Network doctors were presented with different data on Wednesday, predicting 300 acute care beds and approximately 60 ICU beds would be needed once the state reopens its borders.

According to slides from the Central Adelaide Local Health Network (CALHN) presentation – seen by InDaily – SA Health estimated the state would record approximately 3000 cases, but 85 per cent of those infections could be treated at home, while a further 10 per cent would be transferred to medi-hotels.

Once the state reaches its 90 per cent vaccination target, the SA Health modelling presented to doctors shows over 60 acute care beds and more than 15 ICU beds would be required.

SASMOA says the data was collated by SA Health and presented by CALHN executives the day after the Government released its long-anticipated “COVID-Ready” plan outlining when the state would start lifting restrictions.

The union’s chief industrial officer Bernadette Mulholland told InDaily that there were “significant differences” between the two data sets, causing confusion amongst doctors.

“They are confused as to what they are being told… but they are also confused about why are we going through a number of processes given the new modelling that’s coming out,” she said.

“In fairness to the local health network, they said they hadn’t received the (commissioned University of Adelaide) modelling at that stage and they were predicting the resourcing based on figures that they had seen.

“But certainly, this other modelling that they were using was a much higher demand and impact on our hospital sector.”

Mulholland said it was possible that the data presented to doctors on Wednesday was based on a “worse-case scenario”.

“We won’t know until the borders have come down and we have a much more likely opportunity that there will be greater numbers of COVID patients,” she said.

In a statement, a CALHN spokesperson said its initial planning was based on national modelling using approximate figures, while the South Australian-specific modelling by the University of Adelaide was being finalised.

“We will now review plans and adjust according based on the SA specific modelling,” the spokesperson said.

The Adelaide University study, by Professor Joshua Ross from Adelaide’s School of Mathematical Sciences and Dr Thomas Prowse from the School of Biological Sciences, found that reopening borders at 80 per cent with all existing public health measures retained would see an estimated 27 per cent chance of an ‘outbreak’ – defined as “averaging more than 100 cases per day over any three-day period”.

Under the modelling, the chance of an outbreak occurring if the mask-wearing mandate was removed soars to 64 per cent, with the researchers predicting this to “present risks to being able to manage cases, in particular with respect to ICU capacity”.

Peak Ward Occupancy would hit a median of 70 beds – and as many as 203, with a three per cent chance of demand exceeding 200 ward beds, while the median ICU occupancy peak would be 18 beds, with a 20 per cent chance of exceeding 30.

Under this scenario, the median number of total deaths is modelled at 55.

If South Australia removed all its restrictions for those who are fully vaccinated, the median for total deaths rises to 315, with a range between eight and 424.

Australian Medical Association state branch present Dr Michelle Atchison described the data as “frightening”, saying South Australia’s hospitals were already at 100 per cent capacity.

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“It puts the emphasis on keeping our current public health measures and saying that if our current public health measures continue then we’re probably going to be in a pretty good state of hospital demand and hospital capacity,” she said.

“If our public health measures are relaxed or if people aren’t compliant with public health measures there may well be some over-capacity for our hospitals.

“Anything where modelling starts to say ‘we may not be able to cope’ makes the AMA very anxious.”

Premier Steven Marshall announced last week that borders would reopen on November 23, with broader restrictions to be eased once SA hit a vaccination rate of 90 per cent of the population over 12 – which Marshall predicted would occur before Christmas.

However, the Adelaide University modelling includes a table that suggests while the 80 per cent vaccination rate is expected by late November – albeit after the 23rd – the 90 per cent benchmark is not predicted to be met until January, and even then only for people aged 16 and over.

In a statement to InDaily, Ross and Prowse said “uncertainty exists in when vaccination coverages will be reached”.

They said the graphs used data captured on October 24 and “more up to date data is becoming available all the time”.

“The precise date at which a certain coverage is reached is not overly important to the modelling process itself, it is the vaccination coverage at that point in time which is important,” they said.

“If 80 per cent is reached on 23 November, or slightly before or slightly after, does not matter from a modelling perspective, as long as borders are assumed to be opened at 80 per cent (16+) vaccination coverage.

“Our forecasts are continually updated based upon the most recent data.

“In general, recent data has shifted earlier the dates at which various vaccination coverages will be reached.”

Atchison said it was not guaranteed that South Australia would reach its 80 per cent vaccination target by November 23 and doctors were concerned about the imminent surge in COVID cases.

But Business SA policy director Andrew McKenna said businesses “do need a level of certainty around these dates, particularly for international borders”.

“What we’re more concerned about is hitting that 90 per cent (rate) because without a broader (vaccine) mandate we might not actually get to that 90 per cent rate, or if we do, it might be much further than Christmas as indicated by the modelling,” he said.

“If it’s into January already, that’s of some concern.”

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