An experimental bird flu vaccine has failed to protect chickens against the deadly virus, its Australian makers say.

Only a small percentage of the chickens inoculated in the first Australian trial of a possible bird flu vaccine survived when exposed to the H5N1 virus, biopharmaceutical company Imugene said.

"These are not the results we hoped for but we will now use this experience to develop a second avian influenza vaccine candidate," Imugene managing director Dr Warwick Lamb said.

"Although we only have very early data, we have identified ways to make the next trial vaccine candidate more effective."

Developing a totally new vaccine against a disease as virulent as H5N1 was a "major challenge", he said.

"Realistically, vaccine development frequently requires evaluation of several candidates," Dr Lamb added.

Late last month the United States government announced plans to produce supplies of an experimental vaccine against H5N1 based on a genetically-modified version, even though it has not been tested in humans.

Previous CSIRO research showed that the Australian-developed anti-viral drug, Relenza, prevented the bird flu virus from multiplying.

More than 40 people have caught the virus from birds in Asia since late last year.