COVID vaccines begin to reduce hospitalisations

NSW’s strategy of pouring vaccines into COVID-19 outbreak areas is paying off, with about a third of new cases fighting their infection with some level of protection against severe disease.

Immunisation and treatment innovations could keep the state’s intensive care cases well below numbers predicted by the Burnet Institute last month, infectious disease experts say.

According to NSW Health’s regular COVID-19 surveillance report, more than 35 per cent of people who tested positive to the virus in the week ending September 11 had received at least one dose of a vaccine. About one in 20 cases were fully vaccinated.

There were 1155 COVID-19 cases in hospital in NSW on Monday, including 214 people in intensive care. A week earlier, there were 1207 hospitalised cases and 236 in intensive care.

Modelling by the Burnet Institute, a Melbourne-based medical research organisation, published by the state government last month suggested NSW Health could be treating 560 COVID-19 patients in intensive care by the end of October.

NSW Health confirmed on Monday the modelling did factor in rising vaccination rates, but rates had increased more quickly than were modelled.

“Pleasingly the hospitalisation rate has not been as high as we had seen in the modelling and the ICU admissions have been a bit lower as well but it doesn’t mean we are out of the woods in terms of overwhelming our hospitals,” Premier Gladys Berejiklian said.

However, the number of virus patients being treated – and dying – in their homes is rising. There have been 29 people who have died at home with COVID-19 during the Delta outbreak, including at least 13 since September 15. Sixteen tested positive after their death.

Data from September 22 showed 14,447 COVID-19 patients were being cared for outside a hospital setting, up from 13,590 the previous week.

Professor Greg Dore, an infectious disease physician at St Vincent’s Hospital, said rising vaccination rates had “clearly” made an impact on hospitalisation and intensive care numbers.

“We know that there’s a 70 to 90 per cent reduction in hospitalisation with a single dose of AstraZeneca or Pfizer, and that is being reflected in the numbers,” he said.

Professor Dore said he thought the situation in hospitals was “considerably less bleak” than the modelling suggested.

“The progression to intensive care requirement by a patient has absolutely been slowed down by vaccination,” he said. “It is pretty good news in terms of stabilising hospitalisation numbers a month earlier than projected.”

He said improvements in treatments for COVID-19 patients – such as the provisional approval of sotrovimab, a one-dose intravenal antibody treatment shown to reduce the risk of severe disease, may also have played a small role.

“The numbers aren’t huge, but that may be having some sort of impact as well,” Professor Dore said.

Professor Tony Cunningham, co-director of the Centre for Virus Research at the Westmead Institute for Medical Research, agreed the impact of vaccination and improved treatment was being seen.

Given one dose of COVID-19 vaccine is less effective against the Delta variant than earlier strains of the virus, he said the focus needed to be increasing second-dose coverage by administering AstraZeneca four to eight weeks apart and bringing forward Pfizer doses initially scheduled to be administered on eight-week intervals where possible.

Of the 236 cases in intensive care on Monday, 46 had received one dose of a vaccine and 161 were not vaccinated.

“It really behoves us to get two doses into people as quickly as possible,” Professor Cunningham said of the intensive care rates. “Hopefully, now we’ve got enough Pfizer supply, we can go back to a shorter dose interval rather than stretching it out to eight weeks. I think that’s critical.”

Hospitalisation tends to lag about 10 days behind case numbers, said ANU infectious diseases physician Professor Peter Collignon, who views the state’s hospitalisation rate as a reflection of both rising vaccination rates and the case peak earlier this month.

“The good news is case numbers appear to be turning, and that’s a function, also, of vaccination,” he said.

Professor Collignon said it was important for the public to understand that breakthrough infections – infections in vaccinated people – would happen, noting hospitalisation in vaccinated cases should be viewed in the context of a patient’s age and health conditions.

University of Sydney professor of biostatistics Ian Marschner, who has been modelling the ongoing mortality of COVID-19 in NSW, said the outbreak had a mortality rate comparable to an unvaccinated population until the beginning of September, when numbers started to shift.

“We are now starting to see what we refer to as ‘mortality deficits’: less mortality than would be expected in the population of cases,” he said.

with Lucy Carroll

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