What if you only had to get a flu shot once every ten years, or even longer?

The 2009 H1N1 virus may have brought scientists one step closer to developing a “universal vaccine” — offering protection against a wide range of influenza strains over a long period of time.

Researchers used blood samples from patients infected with 2009 H1N1 to develop antibodies in cell cultures.

“What we found was that these individuals made antibodies which were highly cross-reactive against many different influenza virus strains,” said Rafi Ahmed, director of the Emory University Vaccine Center and one of the authors of a study published online this morning in The Journal of Experimental Medicine. “What that means is that this infection induced a response that can protect these people against many different strains of influenza virus.”

The antibodies offer protection against H1N1 viruses in circulation over the past 10 years, as well as the deadly 1918 pandemic flu and H5N1 “bird flu.”

This type of immune response is rarely seen in patients after an outbreak of seasonal flu or after receiving standard flu shots.

Researchers believe the difference may lie in the unusual tendency of 2009 H1N1 antibodies to react with the “stalk” — a portion of the flu virus that shows little variation between strains, as opposed to other parts of the virus which change significantly from year to year.

“The stalk would be the Achilles’ heel,” Ahmed said. “If one can target the immune response towards the stalk, then one would have fairly broad protection against different flu strains. And that will be the goal of the vaccine strategy.”

Currently, the seasonal flu vaccine is updated each year to protect against the three influenza viruses that public health experts believe will be most common during the upcoming season.

If researchers are able to develop a vaccine that produces a similar immune response to what they’ve observed in the lab with 2009 H1N1 antibodies, it could potentially reduce the number of immunizations people need, and the time and cost involved with bringing vaccine to market each year.

Ahmed predicted the annual flu vaccination may, one day, become more like a tetanus shot, which is administered once every ten years. But he cautioned that the study published today involved samples from a small number of patients who became infected with 2009 H1N1.

Because the study did not involve healthy people who received H1N1 immunizations, it remains unclear whether vaccines, which use “killed” or weakened viruses, produce the same crossover protection.

Ahmed predicted the development of a “universal” flu vaccine may still be several years away. However, his study offers hope that such an endeavor is possible.

In addition to the potential to improve vaccines, the study may help researchers develop new treatments for people with severe cases of flu.

The study found that the antibodies protected mice from H1N1, even when administered 72 hours after infection. Researchers said this suggests the antibodies could provide effective therapies for high-risk flu patients, such as people with compromised immune systems and the elderly.