A woman sells ducks at a market in Cairo April 8, 3007. (Xinhua/Reuters File Photo)

    BEIJING, April 18 (Xinhuanet) -- U.S. Food and Drug Administration on Tuesday approved a bird flu vaccine, the first of its kind with U.S. approval.

    The Sanofi-Aventis vaccine could be used to prevent people from becoming infected with the H5N1 bird flu virus. It would be used if the strain mutated into a form that spreads easily from person to person, sparking a pandemic, according to media reports.

    Norman Baylor, director of the FDA's Office of Vaccines Research and Review, said the vaccine is "sort of an interim measure" until better ones are developed.

    "The threat of an influenza pandemic is, at present, one of the most significant public health issues our nation and world faces," FDA commissioner Dr. Andrew von Eschenbach said. "The approval of this vaccine is an important step forward in our protection against a pandemic."

    The vaccine will not be sold commercially. The government plans to buy and stockpile enough bird flu vaccine for 20 million people, including emergency and health care workers.

    In a clinical trial, the two-shot series appeared to provide protection to just 45 percent of adults who received the highest dose.

    The H5N1 avian influenza virus has killed 172 people out of 291 known to have been infected, according to the World Health Organization.

    (Agencies)