An "all in one" flu vaccine that protects against several strains of the virus could be used in humans as early as 2013.
Researchers in the US believe a vaccine that has already been tested on animals, primed with influenza DNA before being given a "booster" containing a regular seasonal flu vaccine, could be tested on humans by 2013.
The technique, similar to vaccination methods already employed for diseases such as hepatitis, was found to be effective against a number of strains of the virus, including one from 1934.
After being primed with a vaccine from a 1999 virus, the test subjects developed antibodies that went on to neutralise other strains of the virus that occurred before the original primer.
Among those that it was effective against was the N5NI "bird flu" virus, the study, published in the journal Science found.
Study leader Dr Gary Nabel, from the US National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, said: "We are excited by these results. The prime-boost approach opens a new door to vaccinations for influenza that would be similar to vaccination against such diseases as hepatitis, where we vaccinate early in life and then boost immunity through occasional, additional inoculations in adulthood."