Free flu jabs will be available to residents for an extra two and a half weeks due to concerns about low vaccination rates across the state, especially among children.
The NSW government offered the free vaccinations for the month of June, but has now extended that to July 17.
Health Minister Brad Hazzard said one in four children aged under five had had a flu shot, while 18 per cent of children aged five to 15 had been vaccinated this year.
"These numbers are particularly concerning given in the last month, four times as many kids have been admitted to Sydney's two children's hospitals with flu than with COVID," Mr Hazzard said.
Fewer than 40 per cent of 50 to 65-year-olds and 64 per cent of those over 65 have had their shot.
"More than 1000 people presented to our EDs with flu-like illness last week and almost 165 were so unwell they were admitted, including very young children," NSW chief health officer Dr Kerry Chant said.
"Please take advantage of the offer of the free vaccination to protect yourself against the flu this winter."
The free flu shots are available at GPs for everyone aged six months and over, and at pharmacies for those aged five and over.
Sign up for our newsletter to stay up to date.