A universal flu vaccine comes closer after promising trials in animals, scientists have announced.
According to researchers, the vaccine would give life-long protection against any type of flu.
That should remove the problem with current flu vaccines which must be given anew each year because they focus on the mutating part of the virus.
The proof-of-concept work is published in Science journal and Nature Medicine.
The US studies are now needed in humans to confirm that the method will work in man.
In the meantime, experts say people should continue to receive an annual flu jab because vaccination is still the best way to protect yourself against infection.
Conventional flu jabs target molecules on the surface of the flu virus, but these are constantly changing.
It is the stems that scientists are now focusing on as a target for a universal flu jab.