The FDA ( Food and Drug Administration ) and CDC ( Centers for Disease Control and Prevention ) routinely monitor the safety of all U.S. vaccines by using several vaccine safety surveillance systems, including the Vaccine Adverse Event Reporting System ( VAERS ). VAERS collects and analyzes information from reported adverse events ( health problems or possible side effects ) that occur after vaccination.

FDA and CDC have recently detected an increase in the number of reports to VAERS of febrile seizures following vaccination with Fluzone ( trivalent inactivated influenza vaccine or TIV ).

Fluzone is the only influenza vaccine recommended for use for the 2010-2011 flu season in infants and children 6-23 months of age. These reported febrile seizures have primarily been seen in children younger than 2 years of age. Data from VAERS are preliminary and serve as a sign or indication that further investigation is warranted.

Further investigations are under way to assess whether there could be an association between influenza vaccination and febrile seizures, or if other factors could be involved.

FDA and CDC have seen no increase in VAERS reports of febrile seizures in people older than 2 years of age following vaccination with TIV, and no increase after live attenuated influenza vaccine ( FluMist, the nasal spray vaccine ). In the cases reported, all children recovered and no lasting effects have been seen. Recommendations for the use of flu vaccine in children have not changed.

In some children, having a fever can cause a seizure. Although febrile seizures can be frightening for the child's caregivers, nearly all children who have a febrile seizure recover quickly and have no long term effects. Febrile seizures may occur with any common childhood illnesses that may cause fever, such as ear infections, colds, influenza and other viral infections, and they sometimes happen after vaccination. With regard to influenza infection, one study estimated that seizures occur in 1% of children under 5 years of age with laboratory-confirmed influenza and 9% of children who are hospitalized due to influenza virus infection.
Approximately 1 in 25 ( 4% ) young children will have at least one febrile seizure in their lifetime usually between 6 months and 5 years of age with the peak age between 14 and 18 months of age.

The risk of severe influenza illness is higher among young children, especially children under 2 years of age. Approximately 9 out of 10,000 children 6-23 months of age require hospitalization each season for reasons related to influenza.

Source: FDA, 2011

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