The yearly influenza vaccine that health officials urge people to get each fall might also offer certain individuals some cross protection against the H5N1 virus, commonly known as bird flu, according to investigators at St. Jude Children's Research Hospital.
The investigators found that a protein present in the annual influenza shot can act as a vaccine itself and trigger some cross protection against H5N1 in mice; and that some human volunteers already had antibodies directed against the same part of this virus. Cross protection occurs when the immune response triggered by a vaccine designed to protect against one germ also offers some protection against a different germ.
The finding also suggests that the annual influenza vaccine might be especially beneficial to populations in areas of the world where H5N1 routinely infects birds and poses a threat to people.
"The jury is still out on whether the seasonal flu vaccine is definitely a reliable way to offer people some protection from H5N1," said Richard J. Webby, Ph.D., assistant member in the Virology division of the Department of Infectious Diseases at St. Jude. "But our initial results suggest that this is a research trail worth following." Webby is senior author of the report that appears in the Feb. 13 issue of the online journal PLoS Medicine at www.plosmedicine.org.
The key to the apparent cross protection against H5N1 provided by the human influenza vaccine appears to be the antibodies produced in response to a protein called neuraminidase on the surface of the virus. Neuraminidase, which is noted as "N" in the names of viruses, is one of the major proteins on the surface of human and avian influenza viruses; and it can often be found in human influenza vaccines. However, the amount of "N" in an influenza vaccine can vary widely depending on the company that produces it.