Influenza is a serious disease It is caused by a virus that spreads form infected persons to the nose or throat of others. Most people are ill with this for only a few days, but some get much sicker and may need to be hospitalized.
Influenza causes thousands of deaths each year, mostly among the elderly.
The viruses that cause influenza change often. Because of this, influenza vaccine is updated each year by replacing at least one of the vaccine viruses with a newer one. Protection develops about 2 weeks after the shot and may last up to a year. People at risk for getting a serious case of influenza or complications , or people in close contact with them should get the vaccine. Residents of long term care facilities housing persons with chronic medical conditions.