MODEL RELEASED. Influenza vaccination being injected by a nurse into a patient’s upper arm in a residential care home. This vaccine is for the northern hemisphere in the 20011/12 flu season. It contains three strains of the influenza (flu) virus that stimulate the body’s immune system to produce antibodies, but without causing an infection. The immune system can then respond quickly against future infections by the flu virus. The flu vaccine is given to people at risk, such as the elderly and very young. It is provided annually because of the need to protect against new strains. The vaccine used here is called Enzira.