Parents in New South Wales are being urged to take up the offer of a free flu shot for their children after a child died from the same strain of influenza which caused the 2009 pandemic.

The child, aged under five, was not vaccinated and among 19 admitted to Sydney Children’s hospital at Westmead between 3 April and 8 July 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.

The government agency said it had been a slow start to the flu season in NSW, with 256 cases confirmed in the week ending 8 July, compared with 6,449 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.

The NSW Health chief health officer, Kerry Chant, said there were “plentiful” supplies available of the free flu jab for under-five-year-olds.