The vaccine for the 2009-2010 seasonal influenza contains:

an A/Brisbane/59/2007 (H1N1)-like virus an A/Brisbane/10/2007 (H3N2)-like virus a B/Brisbane/60/2008-like virus

There is always a possibility of a less than optimal match between the virus strains predicted to circulate and the virus strains that end up causing the most illness. Even if the vaccine and the circulating strains are not an exact match, the vaccine may reduce the severity of the illness or may help prevent influenza-related complications.

According to the CDC, between 5 percent and 20 percent of the U.S. population develops influenza each year. More than 200,000 are hospitalized from its complications and about 36,000 people die. Older people, young children, and people with chronic medical conditions are at higher risk for influenza-related complications. Vaccination of these groups is critical.

Additionally, influenza immunization of health care personnel is important in protecting them and others from influenza.

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