One vaccine could protect people, pets and farm animals from bird flu, according to a new study.

A study in the November issue of the Journal of General Virology says that the vaccine works against various strains of the virus in mammals and can even be given to birds in the egg.

By vaccinating eggs against influenza, a researcher said, health officials could protect wild bird species as well as domestic chickens against pandemic flu strains, limiting the spread of disease to humans.

"The world is experiencing a pandemic of influenza in birds caused by an H5N1 virus. Although it has been restricted to Eurasia and some countries in Africa, there is a risk that this virus may spread worldwide," said Daniel Perez of the University of Maryland. "To prepare for a pandemic, it would be ideal to have a vaccine that could be used in multiple animal species."

Researchers modified another strain of influenza, H9N2, to make it less pathogenic so it could serve as a vaccine. All vaccinated mice treated with it survived infection with the strain that caused the 1918 Spanish flu, as well as bird flu.