There are concerns current efforts to prevent flu in children with chronic lung conditions such as asthma are ineffective.

Children with asthma and other chronic lung conditions like cystic fibrosis are five times more likely to be admitted to hospital with the flu, researchers have warned.

To keep them out of hospital this Winter, parents are being reminded of the importance of the flu vaccination.

"Flu is a significant infection in children with chronic lung disease, and can be severe even in otherwise healthy children," said Professor Allen Cheng, Director of the Infection Prevention and Healthcare Epidemiology Unit at Alfred Health and World Health Organisation (WHO) Technical Advisor.

"Flu vaccination is the most simple and effective way to protect your children. The vaccines are provided free for children with chronic illnesses and in some states, they are free for all children in 2018," he said.

A new study, to be presented at a major lung and respiratory conference in Adelaide on Tuesday, shows not only are children with chronic lung disease substantially more at risk of hospitalisation from flu, but the average cost of these hospitalisation is also significantly greater.

The University of NSW and Sydney Children's Hospital study looked at a cohort of 9708 children with chronic lung diseases and 877,240 standard-risk children.

It found the average direct health care cost of each flu hospitalisation to be $19,000 for children with a chronic lung condition compared to $5000 in children without - almost four times higher.

In addition, 13 per cent of chronic lung condition children with flu hospitalisation will require referral to another hospital for ongoing care compared to 7 per cent without.

Hospitalisation was highest in children 0-2 years of age.

Lead researcher Dr Nusrat Homair from the School of Women's and Children's Health, UNSW says the concerning findings support calls for a universal influenza vaccine for these and other children.

"Our research suggests that current efforts to prevent flu in children with chronic lung conditions are either sub-optimal or ineffective," said Dr Homair.

"Although Australian children with chronic lung disease are entitled to free flu vaccination, the uptake - particularly in children with asthma - is reported to very be low. As an immediate first step further research is required to understand the vaccine effectiveness in these children and ways to improve vaccine uptake," she said.