A traditional flu vaccine uses the external proteins on a flu virus (the H and N on strains such as H1N1 and H3N2) to prompt the body's immune system to create antibodies. These proteins, however, are different across different strains and they are liable to mutate, making immune responses from vaccines limited.
However, there are two proteins inside the flu virus that are much more similar across strains and less liable to change over time. Nucleoprotein and matrix protein 1 are more than 90% identical in all strains of influenza A.
Sarah Gilbert from the Jenner Institute in the United Kingdom explains:
"In the nucleoprotein is wrapped around the viral RNA, there's quite a lot of it in flu virus and infected cells. It's essential for the virus because, if it doesn't have the nucleoprotein, its genome isn't stable. It can't do without it and it can't change it very much because it has a particular function and, if it mutates, it won't work. Matrix protein 1 is a structural protein which is part of the inside of the shell around the virus."
If used widely a universal flu vaccine could prevent pandemics, such as the swine flu outbreaks of recent years, and end the need for a seasonal flu jab as mentioned.
Flu viruses mutate yearly, making annual vaccines obsolete after a flu season is over. Frank Collins, Director of the National Institutes of Health commented:
"There are parts of the viral coat that don't change. If you designed a vaccine to go after the constant part of the virus, you'd be protected against all strains. A few years ago such a vaccine seemed completely out of reach."
Adrian Hill, director of the Jenner Institute adds:
"The problem with flu is that you've got lots of different strains and they keep changing. Occasionally one comes out of wildfowl or pigs and we're not immune to it. We need new vaccines and we can't make them fast enough."
Scientists at the National Institute of Allergy and Infectious Diseases (NIAID) are working to develop a universal influenza vaccine, and report that in recent experiments with mice, ferrets and monkeys, researchers at NIAID's Vaccine Research Center used a two-step immunization approach to elicit antibodies that attacked a variety of influenza virus strains.
NIAID Director Anthony S. Fauci, M.D. concludes:
"Generating broadly neutralizing antibodies to multiple strains of influenza in animals through vaccination is an important milestone in the quest for a universal influenza vaccine. This significant advance lays the groundwork for the development of a vaccine to provide long-lasting protection against any strain of influenza. A durable and effective universal influenza vaccine would have enormous ramifications for the control of influenza, a disease that claims an estimated 250,000 to 500,000 lives annually, including an average of 36,000 in the United States."