CDC - Seasonal Influenza (Flu) - Questions and Answers - 2010-2011 Seasonal Influenza (Flu) Vaccine Safety

Questions and Answers
2010-2011 Seasonal Influenza (Flu) Vaccine Safety
What’s in the 2010-2011 seasonal flu vaccine and why?
Each year, the seasonal influenza vaccine contains three influenza viruses – one influenza A (H3N2) virus, one influenza A (H1N1) virus, and one influenza B virus. The 2009 H1N1 influenza virus strain is included in the 2010-2011 seasonal flu vaccine because scientists continue to see this virus strain circulate in the U.S.

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CDC - Seasonal Influenza (Flu) - Questions and Answers - 2010-2011 Seasonal Influenza (Flu) Vaccine Safety