A new flu vaccine which protects against all strains of influenza has had promising results in trials.
Researchers say the vaccine's promise of universal protection could help contain a flu pandemic as it protects against all strains of influenza A, the type invariably responsible for pandemics.
B-strains, which are found only in humans, may cause epidemics but have never caused pandemics.
The vaccine apparently has a significant advantage over existing ones in that it does not have to be reformulated each year to match the prevalent strains of flu and it can be produced by cell culture.
It could therefore easily be stockpiled and used as soon as a pandemic strain emerges.
To date results in human volunteers have shown that the Acam-Flu-A vaccine made by Acambis is safe and produces an immune response against a small protein (peptide) called M2e that is found on the surface of all A-strains of the flu virus.
The vaccine was also tested on ferrets, which are often used in flu research because they are susceptible to human and bird flu.
When the ferrets were divided into two groups - vaccinated with the new vaccine or left unvaccinated - after exposure to a large dose of the H5N1 bird flu, all the unvaccinated ferrets died, but 70 per cent of the vaccinated ones survived.
One of the biggest problems with conventional vaccines is that they target parts of the flu virus that can change rapidly.
Every flu season the World Health Organisation identifies the three strains that are circulating, normally two A-strains and one B, and the vaccine is made to order to provide protection against them.
This becomes a race against time, because millions of eggs have to be produced to grow the vaccine and if it is not used it is out of date by the following season.
The Acambis's enterprise identified some aspect of the virus that remains unchanged - a peptide, M2e, on the surface of all A-strains and then developed a vaccine that targeted it.