People who are allergic to eggs or chicken should probably not receive an influenza vaccine, as chicken eggs are used in the production process. Also, those who had an allergic reaction to a past influenza vaccine should not receive it. Anyone who developed Guillain-Barre syndrome after getting the flu vaccine in a previous year, should not receive additional influenza vaccinations. Also, people who have illnesses or fever at the time of vaccination may need to wait until these go away before getting the vaccine. Children younger than six months of age should not get the flu vaccine.