NSW health authorities are urging parents to take up the offer of a free flu shot for their kids after a child died from influenza.
The child, aged under five, was not vaccinated and among 19 admitted to Sydney Children's Hospital at Westmead between April 3 and July 8 with the flu.
Only two of those were fully vaccinated, NSW Health said.
It was the first child death of the 2018 flu season, caused by influenza A - which was at the centre of the 2009 pandemic.
"Young children don't have immunity to the flu between that age of six months and five years," NSW's Chief Health Officer Kerry Chant told reporters in Sydney on Friday.
"Influenza can have a spectrum but it is actually a significant disease, causing hospitalisation and in tragic circumstances also death."
The government agency says it's been a slow start to the flu season in NSW, with 256 cases confirmed in the week ending July 8, compared with 6449 cases in the equivalent week in 2017.
Almost all of the 256 cases had contracted influenza A, the key strain circulating in NSW and mostly striking children and young adults.
"There are plentiful supplies of the free flu vaccination for under-fives, just call ahead to your GP to check they have it in stock or give them time to order more vaccines," Dr Chant said.