While there have not been any cases of bird flu in the United States, the government will stockpile the vaccine in preparation for a bird flu pandemic.
Experts say this vaccine will provide protection for high risk individuals while another vaccine that fights the circulating strain of bird flu is developed.
Calling the vaccine an important first step forward in the protection against a potential pandemic, the FDA approved the first h5n1 vaccine, to be used if the bird flu mutates into a form that could spread easily from person to person.
In a clinical trial, the FDA says the highest dose of the two-shot vaccine triggered an immune response strong enough to offer some protection to 45 percent of the adults in the study.
That's compared to 90 percent protection offered by the single dose seasonal flu shot.
However, officials say it is better than no protection and they are hoping it will be enough to slow the spread of disease while scientists work to develop a vaccine that better matches the pandemic strain.
Side effects were mild and included pain at the injection side, fatigue and headache.
The “Sanofi Aventis” vaccine is being stockpiled for government use in case of a human outbreak of bird flu and will not be available to the public.
While there has been no reported human case of h5n1 infection in the United States, almost 300 people have been infected worldwide since 2003, more than half have died.
Public health officials say it is important to remember that there is no pandemic underway and that the bird flu virus has not changed into a form that spreads easily among people.