Tests on mice have shown inhaling a protein that increases immune system activity could help combat flu.
Mice given lethal levels of the virus by researchers in the US survived, and saw their symptoms lessen with the treatment.
It means an aerosol taken nasally by human flu patients has great potential, they said in the American Journal of Respiratory and Critical Care Medicine.
A British flu expert said the tests could help set the direction of future flu research, even if effects on mice are not replicated in humans.
Flu is a factor in around 250,000 and 500,000 deaths every year, with three to five million people suffering symptoms in that time, the World Health Organization said.
The vaccines made every year - which combat the most common type of the evolving virus at that time - are only variably effective, the researchers said.
Alveolar macrophages (AM) are the first immune response areas that can fight inhaled molecules and organisms. Granulocyte macrophage-colony stimulating factor (GM-CSF) increases their activity and the US study looked at how it might help fight flu.
Mice were given high doses of a flu virus, and those treated with GM-CSF were compared with a group not given any treatment.
All the untreated animals shed weight and died a few days after getting the virus, but all the mice given GM-CSF survived. That group also lost weight, but returned to normal shortly afterwards.
The researchers saw the same results with a number of strains of flu, including swine flu (H1N1).