Do I need to get the flu shot every year?

The flu shot is needed every season for two reasons.

When we get the flu shot, our immune system produces antibodies to protect us against the viruses included in the influenza vaccine. 

These antibody levels may decline over time, so if the vaccine composition for the upcoming flu season remains unchanged, getting the flu shot yearly is recommended.

Also, the strain of the flu virus changes over time, so it is important to stay current and get vaccinated yearly.