South Australia can expect the next wave of COVID-19 cases to peak in early December, with the highest number of hospitalisations to come in the days around Christmas, a parliamentary committee has heard.
The state's COVID-19 Direction Accountability and Oversight Committee has received evidence from University of Adelaide mathematics professor Joshua Ross, who has previously prepared modelling for the state government's Emergency Management Council.
He told the committee he handed new modelling over to Chief Public Health Officer Nicola Spurrier "late last night or in the early hours of the morning".
"This [committee evidence] is probably before our government has seen this," he said.
"In terms of the peak infections, it'll be somewhere between 6,000 to 8,000… [in early December] … and obviously the hospitalisations lag by about two weeks.
"Hospitalisations … [are expected to be] similar to what we've seen in the first wave, around 200 total occupancy.
"It's less than we've experienced in previous waves."
Professor Ross said increased "hybrid immunity" in those who have already recovered from the virus, and who have also received all of their vaccinations, would put the state's health system in a better position than in previous waves.
"With maintenance of adequate vaccine uptake, and hybrid immunity which happens incidentally to that, it's reasonable to believe that SA is past the worst in terms of the demand on hospitals that we will see," he said.
"However, it is possible that a new variant will emerge that could significantly escape immunity … so I think that we should consider … that we may need to put some restrictions back in place if it looks like it's going to be particularly bad.
"But I think the focus needs to remain on vaccines."
He said the coming wave would be "mostly a consequence of waning immunity, as opposed to a new variant".
'Lots of uncertainty'
The modelling is based on the same level of restrictions that will be in place from this coming Friday, when mandatory isolation rules for COVID-positive people are dropped.
Previous projections had placed the next case peak in November, but Mr Ross told the committee he was updating the modelling "typically a couple of times a week".
"There's lots of uncertainty around what's going to happen with variants and I'm doing my best to try to account for what I think they will do," he said.
"In the last five or six weeks, BA.2.75 looked like … it was going to take off … but now it's actually starting to come down.
"That could be down to chance, or it could be down to something that we're still learning about the immunity we have in the population against certain variants.
"But [all of that] can result to changes of a week or two in terms of the timing of peaks.
"The uncertainty reduces as we get closer and closer, so at least two or three weeks before it's actually due to happen, there should be more certainty."
Professor Ross said the state government should continue to engage in surveillance of COVID-19 cases, whether through industry-specific testing or wastewater sampling, as fewer people undertook testing.
