"I'm fairly certain we will have a vaccine, but will the virus change to the point of our vaccine not being as protective as we would like it to be?" asks Anthony Fauci, Director at the National Center for Immunization and Respiratory Diseases. Although the virus has not changed since early April, "every time you talk about influenza, you must prepare for the unpredictable," he says. (0:35) Listen
If H1N1 Changes, Current Vaccine Won't Work, Says Expert
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