FDA Postlicensure Rapid Immunization Safety Monitoring (PRISM) Study Demonstrates No Statistically Significant Association between Trivalent Inactivated Influenza Vaccine and Febrile Seizures in Children during the 2010-2011 Influenza Season

Basic Details
Friday, May 16, 2014
Communication Type
Safety Communication
FDA Center
Medical Product
influenza vaccine
trivalent inactivated influenza vaccine (TIV)
Health Outcome(s)
febrile seizure
This information supersedes the FDA Communication issued on January 20, 2011
During the 2010-2011 influenza season, the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention communicated to the public that an increased number of reports of febrile seizures following vaccination with Fluzone (trivalent inactivated influenza vaccine or TIV, manufactured by Sanofi Pasteur, Inc.) were received into the Vaccine Adverse Event Reporting System (VAERS). 
Although VAERS can provide early indications of possible safety concerns, epidemiologic studies are necessary to determine whether adverse events are occurring more often than expected in people who receive a vaccine. To further investigate febrile seizures after vaccination with Fluzone as well as other TIVs administered to children less than 5 years of age during the 2010-2011 influenza season, FDA initiated a study using its Mini-Sentinel Postlicensure Rapid Immunization Safety Monitoring (PRISM) program, the largest vaccine safety surveillance program in the United States.[1] The study identified 1.9 million children aged 6 through 59 months who were enrolled in one of three health plans from July 1, 2010 to June 30, 2011. From this total, 842,325 met eligibility criteria ensuring that sufficient pre-vaccination and follow-up information would be available to investigators, with 68 confirmed cases of febrile seizures identified within 20 days after receipt of TIV. The study showed no statistically significant association between TIVs and increased risk of febrile seizures. Fluzone is the most widely used TIV in the U.S. in the age group that was included in the study. Based on these findings, FDA is not requesting changes to the Prescribing Information for Fluzone or any of the other influenza vaccines. The benefits of vaccination with Fluzone and other influenza vaccines are substantial and they have been safely used for decades.
About Influenza and Influenza Vaccination
The risk of severe influenza illness is increased among young children, especially children under 2 years of age. Approximately 9 out of 10,000 children 6 through 23 months of age require hospitalization each season for reasons related to influenza. Influenza vaccine is the best way to protect against becoming ill with influenza, and it is recommended that all persons ages 6 months and older receive an influenza vaccine each year.[2]
Information on Febrile Seizures
Febrile means "relating to a fever” or an unusually high body temperature. 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 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.[3]
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.
Parents and caregivers should contact their child’s health care provider if they have any questions or concerns about their child’s health.
[3] Poehling KA, Edwards KM, Weinberg GA, Szilaglyi P, Staat MA, Iwane MK, et al. The underrecognized burden of influenza in young children. N Engl J Med. 2006 Jul 6;355(1):31-40.