The flu vaccine must be given every year because the vaccine is different each season. The flu vaccine contains 3 strains of killed influenza virus that have been identified to cause the illness for that year. The best time to receive the vaccine is October through November of each year. The flu vaccine is safe for almost everyone. The preservative used in the flu vaccine is Thimerasol.
Some people experience a few minor side effects from the flu vaccine.
More serious side effects, associated with Guillain-Barre Syndrome, were reported in 1976 with the swine flu vaccine. There has been no increase incidence of Guillain-Barre Syndrome since that time. Because the flu vaccine has been grown on egg protein, the flu vaccine is not recommended for people who have a history of severe egg allergy. However, if you have been able to eat eggs, it may be possible for you to receive the flu vaccine. Many people who believe they are allergic to eggs tolerate the flu vaccine.