A new wave of Covid-19 infections is looming in New South Wales, the state’s chief health officer, Dr Kerry Chant, will warn on Thursday, with transmission of the virus predicted to increase in coming weeks.
It follows Victoria’s chief health officer, Prof Brett Sutton, making a similar announcement last week, with Omicron subvariants BQ.1 and XBB tipped to overtake BA.5 as the dominant variants throughout Australia.
Chant is expected on Thursday to reiterate the importance of getting booster doses, and will again urge those most at risk of severe disease to plan ahead by talking to their doctor about the antivirals available to reduce the severity of infection.
She will also urge people to stay home if they have cold or flu-like symptoms and ask those who must leave the house while unwell to wear a mask when indoors or on public transport. They should avoid large gatherings and high-risk settings, such as hospitals and aged or disability care facilities, for at least seven days.
Omicron subvariants BQ.1 and XBB are driving significant cases and hospitalisations overseas due to their ability to escape immunity from past infection – and due to waning immunity from past vaccination.
The World Health Organization does not consider the two subvariants as different enough from other circulating Omicron subvariants to warrant their classification as new variants of concern. But the two sublineages remain part of Omicron, which is a variant of concern.
The WHO has said there is no epidemiological data to suggest an increase in disease severity due to the variants.
“Cases of reinfection were primarily limited to those with initial infection in the pre-Omicron period,” a WHO statement published on 27 October said. “As of now, there are no data to support escape from recent immune responses induced by other Omicron lineages.”
On Saturday, the Victorian premier, Daniel Andrews, said fluctuations in case numbers would continue and “Covid will be with us in one form or another for quite a long time”.
“But we are treating it in a different way now because you’ve got to move beyond this,” he said.
“We’re going to see Covid numbers go up and down. Whether it’s a wave or whether it’s a spike, I’ll leave that for others to determine. This era of Covid exceptionalism has to end, and it has. National cabinet has made those decisions.”
The latest NSW respiratory diseases surveillance report, with an overview of Covid cases, will be published later on Thursday.
Meanwhile, results from two complementary national serosurveys, one in children and adolescents and one in adults, were published on Thursday to provide a snapshot of the extent of infections across Australia to the end of August.
Serosurveys involve conducting tests on blood samples taken from thousands of Australians across various age groups, geographical locations and target populations. Researchers look for antibodies to the virus in the blood to determine the extent a population has been affected.
The children and adolescents survey found at least 64% of 0 to 19-year-olds in Australia had been infected with Covid-19.
Dr Archana Koirala, an infectious disease specialist at the National Centre for Immunisation Research and Surveillance and paediatric study lead, said: “Overall, this study tells us that at least two-thirds of children in Australia have had Covid-19.”
“This is more than double the number of cases reported based on nose and throat swab testing for the virus,” she said. “This is expected since many children have either mild or no symptoms and are therefore not tested for the virus.”
In children aged one to four years old, approximately eight out of 10 had evidence of past infection. This group was not eligible for vaccination at the time of the serosurveys; however, high-risk, severely immunocompromised children aged six months to four years became eligible for vaccination from September.
The adult study found at least 65% of adults in Australia had been infected by the virus, similar to the proportion of children and adolescents.