British biotech company Acambis has focused on one such protein, called M2, whose sequence in human flu viruses has remained the same as far back as the 1918 Spanish flu. The vaccine is effective in mice against various strains of human influenza. Now the company is gearing up to run toxicity studies before starting human trials. Meanwhile, Israeli company BiondVax Pharmaceuticals has a similar strategy, using several stable proteins to boost the immune response.

Both Acambis and BiondVax plan to test their vaccines against avian viruses, which have a slightly different form of the M2 protein. If successful, the companies will speed up the development process. Both companies say their vaccines can be manufactured quickly -- possibly in a matter of weeks -- because they can be made using bacteria rather than grown using the traditional egg-based method.

But it's unclear how well these vaccines will work in people. Some experts say the focus should stay with more traditional strategies, such as surveillance systems to monitor strains as they emerge and faster methods to manufacture traditional flu vaccines.

Even if development of these vaccines goes well, it will be at least several years before they are ready. Biondvax aims to begin human testing in January 2007.

Meanwhile, DNA-based vaccines might provide protection from a pandemic far sooner than a universal vaccine would be ready. Instead of administering a dressed-up protein, as Acambis and BiondVax do, or a safe form of a virus, like traditional vaccines, PowderMed, based in Oxford, UK, is developing a small chunk of DNA that encodes the viral gene for the targeted viral protein. The DNA is shot into cells on the skin, which start making the viral proteins and trigger an antibody response.

Like traditional vaccines, the DNA target sequence would need to be updated for new strains of flu. But because the vaccine is composed of DNA rather than proteins, new genes could be made in a week, says Clive Dix, PowderMed's chief executive officer.

PowderMed has already begun testing on humans. People who have been vaccinated with this method produce the appropriate antibodies and show no safety complications, says Dix. The company is now planning a larger-scale trial, in which participants will be exposed to a flu virus.

Scientists developing any of these new vaccines say they hope to get a financial boost from invigorated interest in the industry. In early November, President Bush announced a pandemic preparedness plan that includes $2.8 billion to support the development of new vaccine technologies.

"We know there will be future pandemics," says Ashley Birkett, director of viral immunology for Acambis. "We see this is a long-term strategy."