It could be years before biopharmaceutical company CSL's flu vaccine can be used again by children, the company says.
CSL's vice-president of medical and research, Darryl Maher, says the company is trying to change the way it manufactures the vaccine, after the 2010 Fluvax inoculation caused fevers and convulsions in some young children.
An intensive two-year investigation into the adverse reactions, released publicly for the first time on Wednesday, found specific virus components had triggered excessive immune responses in children.
Dr Maher said the manufacturing method used by CSL seemed to preserve the virus components that caused the reactions.
He said CSL needed to change the process and show that the new method worked, while providing a safe and effective vaccine for all age groups.
"It's going to take a lot longer to establish safety in young children again," Dr Maher told AAP on Wednesday.
"We'll have to do clinical trials and that's going to take several years."
Dr Maher said the adverse reactions in 2010 were "quite unexpected".
CSL's Fluvax vaccine was banned for use in children under five and is only recommended for at-risk children aged five to nine if no other flu vaccines are available.
The Therapeutic Goods Administration (TGA) approved the use of Fluvax late last year in people over the age of 10.
CSL released the results of its investigations at a national immunisation conference in Darwin.
The conference also heard from Julie Leask of the University of Sydney's School of Public Health who said more pregnant women should be receiving flu vaccinations to protect them and their babies.
Currently, fewer than one-third of pregnant women are vaccinated against the flu, despite being at greater risk of contracting the virus.
"At the moment, Australia needs to vastly improve it pregnancy flu vaccination rates so that pregnant women are protected and their infants are better protected as well," Dr Leask told AAP.
She said there was increasing interest in vaccinating pregnant women against whooping cough and trials were ongoing.
Currently the whooping cough inoculation is recommended only for pregnant women at direct risk of contracting the disease, such as childcare workers.