Researchers have tried to test a protein which targets viruses from every flu family.
These included three pandemic viruses (H1, H2 and H3), three others that attack occasionally (H6, H9 and H7), and the H5N1 bird flu from 2004 - albeit modified to make it less deadly.
Mice were injected with this protein twice, three weeks apart, to allow their immunity to develop. Two weeks after the second injection each mouse was exposed to one type of live flu virus, as were unvaccinated mice, reports New Scientist.
Vaccinated mice still became ill, but not as ill as unvaccinated mice, judging from the weight they lost, a standard measure of illness in mice.
Despite partial protection, the vaccine would be cheap and quick to make, and could stop people dying, the team say - which might be enough in a serious pandemic.
However, since it doesn't prevent illness altogether, people would still need constant re-vaccination to avoid ordinary, seasonal flu.
Swine flu seems to have replaced one formerly common flu virus, from its own H1 family, and it dominated the Australian flu season. But the most deadly pre-pandemic virus, H3N1, remains common in China, south-east Asia and Africa, and has accounted for half the US cases tested this season.
If we could identify a flu protein that the virus can't alter so readily, then we should be able to elicit immunity that recognises all kinds of flu.
The study was published in Proceedings of the National Academy of Sciences.