The flu is caused by influenza viruses which affect the respiratory system, including the nose, throat and lungs. It is a contagious illness that may cause mild to severe illness and, in more extreme cases, can even cause complications that lead to death.
Flu shots are the first and most important step in protecting people of all ages against the flu. The Centers for Disease Control and Prevention recommends that every American over the age of six months get vaccinated.
Flu shots are especially important for seniors, young children and people with certain health conditions who are at higher risk of developing complications from the flu.
Flu season typically peaks from December through February in the United States, but outbreaks can start as early as October and appear as late as May.