What are the side effects of the flu vaccine?
The most serious side effect that can occur after influenza vaccination is an allergic reaction in people who have a severe allergy to eggs. For this reason, people who have an allergy to eggs should not receive the influenza vaccine. The National Center for Infectious Diseases (a division of the Centers for Disease Control and Prevention, CDC) says that influenza vaccine causes no side effects in most people who are not allergic to eggs. Less than one-third of people who receive the vaccine experience some soreness at the vaccination site, and about 5 to 10 percent experience mild side effects, such as headache or low-grade fever for about a day after receiving the vaccination. Because these mild side effects mimic some influenza symptoms, some people believe the influenza vaccine causes them to get influenza.
