Scientists are making a vaccine that could give lifelong protection against all types of flu in a single jab.
The vaccine is aimed to protect against all flu strains
Currently, at risk people in the UK - the elderly and ill - need annual flu jabs, and there is no jab available yet guaranteed to beat bird flu.
Biotechnology firm Acambis, in Cambridge, the UK, says it hopes its jab will target numerous mutations that presently allow flu to evade attack.
However, the work is very early and is years off being tested in humans.
Each year winter flu kills around 4,000 people in the UK.
Globally, between 500,000 and one million people die each year from influenza.
If the bird flu virus currently circulating in Asia were to mutate and spread from person to person it could kill as many people as the 1918 Spanish flu, which claimed between 20 and 40 million lives, experts have warned.
Current flu vaccines work by giving immunity to two proteins called haemagglutinin and neuraminidase, which are found on the surface of flu viruses.
However, these proteins keep mutating which means doctors have to keep making new vaccines to keep up.
Scientists at Acambis' laboratory in the US, together with Belgian researchers at Flanders Interuniversity Institute for Biotechnology, are focusing their efforts on a different protein, called M2, which does not appear to mutate so readily, as well as other technology that they cannot disclose yet for commercial reasons.
If successful, a single shot of the vaccine could protect a person against all strains of influenza virus, they believe.
Dr Thomas Monath, chief scientific officer at Acambis, said: "We aim to avoid the need for annual re-engineering and manufacture of the new product, something that is not yet possible with existing vaccines.
"The need to develop a new vaccine each time a different influenza strain emerges often results in long delays before a population can be protected.
"The technology also has special importance as a potential means of protecting human populations against pandemic influenza strains."
So far the vaccine has only been tested in animals. The scientists said it would take several years before large-scale human trials could be done.
Professor Maria Zambon, a flu expert at the Health Protection Agency, said: " We welcome advances in the process of developing novel flu vaccines and vaccination techniques.
"However this vaccine is still very early in a vaccine development pipeline and it will take some time to establish how this vaccine performs in human trials and whether it can proceed to being licensed for use in the UK."
Professor Karl Nicholson, professor of infectious diseases at Leicester University, said: "It would be enormously helpful to mankind to have just the one vaccine but sadly I think it is a long way off."
He said it might be 10 years before any such product could be ready for widespread use in humans.