Parents are being urged to vaccinate their children against influenza amid a spike in emergency department presentations by previously healthy school-aged kids.
NSW Chief Health Officer Kerry Chant warned flu cases were increasing, placing young people at heightened risk, while the circulation of COVID-19 had waned.
"COVID has settled, we are seeing a decline in circulation, but it doesn't mean that it's not about," Dr Chant told reporters in Sydney on Thursday.
Meanwhile, as winter hits its stride, cases of flu are peaking, particularly influenza B, which tends to have a greater impact on school-aged children.
Last week NSW emergency departments recorded a 37 per cent increase in patients with flu-like illnesses, with more than 50 per cent of them under 16.
Since May, 16 children have been admitted to intensive care at three major hospitals with life-threatening complications from flu, including serious heart, brain and muscle-related issues.
Dr Chant urged parents to get their children vaccinated before school resumes and recommended vaccination become "a family endeavour", with everyone six months and older getting a jab.
"Please get your children vaccinated during these school holidays. The vaccine is their best protection," she said.
Just one in eight schoolchildren in NSW have received a flu vaccination this year, and one in four aged under five.
Children aged from six months to five are eligible for a free flu shot available from a GP.
NSW Chief Pediatrician Matthew O'Meara said it was fortunate there had been no flu deaths this year, but warned "the season is not over".
"We are seeing cases rise,'' Dr O'Meara said.
"We expect there to be more children with influenza and more children with complications of influenza, so now's the time to do something about it."
He said parents should monitor the progress of a child with the flu, and if symptoms worsen to seek help from a GP or at hospital.
"If the child has had a bit of a fever, a cough or runny nose and then the pattern of the illness changes, if you think they're getting worse, you're absolutely right to get help," Dr O'Meara said.
Symptoms include lethargy, drowsiness or irritation, breathing problems, skin discolouration, poor fluid intake and severe pain.
The director of the National Centre for Immunisation, Research and Surveillance, Professor Kristine Macartney, said there was a misconception among parents that the flu was just a runny nose.
"Sometimes the flu can be mild, but in some children it can lead to very serious complications. This includes in previously healthy children," she said.
