the traditional flu shot contains proteins separated from the flu virus. those proteins can't cause illness. but your immune system learns to recognize them and mounts a protective reaction if a real live flu virus tries to infect you. the flumist nasal spray works differently. it contains a live flu virus that has been weakened to the point that it can't cause the flu. that sounds pretty scary but millions of people have safely taken this kind of vaccine. the advantage of the nasal spray is that in children who have never had the flu or a flu vaccine before it seems to elicit a stronger immune response than the flu shot.
what's the difference between the nasal spray and injectable vaccines for flu?