Scientists are beginning clinical trials of a new flu vaccine which could offer long-term protection against multiple strains of the disease, Oxford University has said.

The jab could even make patients immune to human mutations of bird flu in the event of a pandemic.

Currently doctors can only vaccinate against certain strains of flu and the formulation has to be changed every year to cope with the constant changes in the disease.

Dr Sarah Gilbert of the Jenner Institute, University of Oxford, said: "This approach to influenza vaccination is unsatisfactory for use against seasonal influenza and of little use when new types of flu begin to infect humans from birds.

"It leaves manufacturers with a few months to produce the necessary stocks, the vaccine has to be administered to at-risk populations within a short time window, and those receiving the injection will all have to be vaccinated again the following year."

Existing vaccines produce antibodies in reaction to the proteins on the surface of the virus, but these change between strains and over time.

But by changing the way the vaccine works so that it attacks the internal proteins that remain the same, the scientists think they have hit on a vaccine that works for many different strains.

"By targeting the internal proteins of the virus, we can come up with a universal flu jab.

The same vaccine would work against all seasonal flu and protect against bird flu," said Dr Gilbert.

"Children would be protected, we'd see economic benefits through reduced sickness in people of working age, and the elderly, who respond less well to vaccination, would be better off through lack of exposure to flu," she added.

The vaccine is currently being tested on 12 volunteers. If the trial is successful it will require extensive further testing before it can be approved for use by doctors.

The World Health Organisation states that each year flu epidemics result in between three and five million cases of severe illness and between 250,000 and 500,000 deaths around the world.

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