Every year, from 5 to 20 percent of the people in the United States will become infected with influenza virus. An average of 200,000 of these people will require hospitalization and up to 50,000 will die. Older folks over the age of 65 are especially susceptible to influenza infection, since the immune system becomes weaker with age. In addition, older folks are also more susceptible to long-term disability following influenza infection, especially if they are hospitalized.
Last year's seasonal flu vaccine effectiveness was just 42%, the US Centers for Disease Control and Prevention estimated. Even if vaccinated, people had inadequate protection against the flu.