About 70 million people a year get flu shots in the United States, according to the Centers for Disease Control and Prevention.
Currently, the standard flu vaccine is altered every year to keep up with changing virus strains. The vaccine focuses on protein targets on flu viruses, and these targets vary a lot from one strain to the next.
The experimental vaccine uses a different target, one that is virtually identical across strains.
The work is reported by Walter Fiers, a retired professor of molecular biology at the University of Ghent, with colleagues. In interviews, Fiers and American flu experts cautioned that the work is preliminary.
The vaccine focused on the so-called M2 protein of the virus. Researchers immunized the mice with three injections at three-week intervals, and exposed them three weeks later to a large, potentially lethal dose of flu virus.
In one round of the experiments, the vaccine saved eight of 12 mice in one vaccinated group and all 12 in another, while only two of 11 unprotected mice survived. Researchers got about the same results when they squirted the vaccine into the nose rather than injecting it.
Fiers said that with the far lower doses of virus that people normally encounter, he would expect the vaccine to protect people against flu infection, or at least from developing a full-blown case. But it will take studies in people to confirm that.
The standard vaccine is aimed at two categories of influenza virus, called A and B. The study focused on influenza A, which poses the biggest threat to people and forces scientists to change the standard vaccine every year. The influenza B portion of the standard vaccine doesn't have to be altered annually.
Dr. Edwin Kilbourne, a flu expert at the New York Medical College in Valhalla, called M2 vaccines promising but said much more research is needed. Scientists are pursuing other promising approaches for universal flu vaccines too, he said.
He also noted that protection from a flu shot lasts only a year or two.