Japanese researchers said Wednesday they were in the final stage of developing a painless bird flu vaccine which is sprayed up the nose instead of being injected.
The nasal spray could make it easier to vaccinate people in developing countries with limited medical resources, which have borne the brunt of avian influenza since an outbreak in 2003.
Researchers sprayed the vaccine into the noses of mice and monkeys and found it was effective against H5N1, the strain of bird flu that can be deadly for humans, as well as its subtypes.
"It's easier to handle for people in developing countries because you don't need needles," said Hideki Hasegawa, the researcher on the project at the National Institute of Infectious Diseases.
Unlike current vaccines, the nasal spray is also seen as effective in mutations of the H5N1 virus -- meaning it could protect against a potential global pandemic.
The spray counters potential mutations because its antibodies work differently.
The new method "stimulates mucous membranes instead of stimulating cells of the immune system, triggering secreting antibodies on the surface of the mucous membranes," Hasegawa said.
More than 200 people have died, around half of them Indonesia, and poultry flocks have been devastated since avian influenza broke out in 2003.
Human victims have mostly been people in close contact with sick birds. But the World Health Organisation warns that millions of people could die worldwide if the virus mutates into a form easily transmissible among humans.
The Japanese team aims to start clinical trials of the spray on humans as early as 2010.
"But it would take years before our research is put to practical use as a flu vaccine," he said.
Just two days ago, a different team of researchers at the same institute announced that it had paved the way to develop an all-round vaccine to protect people from all strains of bird flu including mutations.
The World Health Organisation said last week that there was no evidence that the bird flu virus has yet mutated into a form that could set off a pandemic.