French drug company Sanofi Pasteur has reported an encouraging start in early clinical trials for a prototype bird flu vaccine.
Many experts think a new flu pandemic is inevitable
It said it had seen a good response from the 300 volunteers trialling the vaccine, laying the basis for further trials and research.
Scientists worldwide are working on a vaccine for the H5N1 bird flu strain.
It is considered the strain most likely to mutate eventually into a deadly human flu that could sweep the world.
It is not possible to perfect a flu vaccine before a pandemic starts because the vaccine must exactly match the strain of influenza, which is not known until it appears.
Even so, Sanofi Pasteur - the vaccines arm of drugs giant Sanofi Aventis - hopes to develop a practical vaccine injection that could be available in large enough quantities to treat a worldwide bird flu outbreak.