Febrile Seizures Following Childhood Vaccinations, Including Influenza Vaccination

What is a febrile seizure?

Febrile means "having a fever." A seizure is a convulsion or fit of uncontrolled body movements. A "febrile seizure" refers to a seizure/convulsion in a child associated with a fever. In children younger than 5 years old, having a fever for any reason (illness, vaccination, etc…) can bring on a febrile seizure. During a febrile seizure, a child often has spasms or jerking movements—large or small—and may lose consciousness. Febrile seizures usually last only a minute or two, and do not cause any permanent neurological damage. They are most common with body temperatures reaching 102°F (38.9°C) or higher, but also can occur at lower body temperatures or when a fever is going down.

Is there an increased risk for febrile seizures after any childhood vaccine?

Febrile seizures can happen with any condition that causes a fever, including typical childhood illnesses like a cold, the flu, an ear infection , or roseola . They are most common after infections, including those that can be prevented by vaccination. There are rare instances where febrile seizures can occur after vaccination.

Is there an increased risk for febrile seizures after children receive an influenza (flu) vaccine?

Febrile seizures can occur when a child is sick with influenza virus infection or other childhood illnesses that may cause fever and therefore are usually seen during cold and flu season in the United States. However, several studies of children in the United States have shown no increased risk for febrile seizures following receipt of seasonal flu vaccines. One study evaluated more than 45,000 children aged 6 months through 23 months of age who received influenza vaccines during 1991 through 2003 and did not find an association with seizures. In addition, there was no indication that seasonal flu vaccines or the 2009 H1N1 flu vaccines used in the United States during the 2009-2010 flu season were associated with an increased risk of febrile seizures. However, during the 2010 influenza season in the Southern Hemisphere, febrile seizures were found to be associated with one formulation of influenza vaccine produced by CSL. Although this vaccine is not recommended for children in the United States, systems are in place to monitor adverse events, including seizures, after seasonal flu vaccines. More information on this situation is available at "CSL Seasonal Influenza Vaccine Safety in the United States".

Who is most at risk for febrile seizures?

Febrile seizures are fairly common. About 2% to 5% of young children will have at least one febrile seizure. Most febrile seizures occur in children between 6 months and 5 years of age. A child who has already had a febrile seizure is more likely to have another one. Also if a member of a child's immediate family (a brother, sister, or parent) has had febrile seizures, that child is more likely to have a febrile seizure.

How serious is a febrile seizure?

The majority of children who have febrile seizures recover quickly and have no lasting effects. However, febrile seizures often result in a visit to an emergency room and can be very frightening for parents and caregivers.

About 1 in 3 children who have one febrile seizure will have at least one more febrile seizure during childhood. Most children (greater than 90%) who have a seizure will not develop epilepsy. Genetic predisposition (i.e., family history) and other factors such as cerebral palsy, delayed development, or other neurological abnormalities increase a child’s risk for developing epilepsy after a febrile seizure.

Can febrile seizures after childhood vaccinations be prevented?

In general, febrile seizures cannot be prevented. Some health care providers recommend aspirin-free fever-reducing medications to make the child more comfortable. However, these medications have not been shown to prevent febrile seizures. To avoid choking, children should not be given medication or anything else by mouth during a seizure.

Can febrile seizures after any childhood vaccination be reported to CDC and FDA?

Anyone can report an adverse event following vaccination to the U.S. Vaccine Adverse Event Reporting System (VAERS). The National Childhood Vaccine Injury Act (NCVIA) requires health care providers to report any adverse event that is listed by the vaccine manufacturer as being a contraindication (reason for not giving the child any further doses of the vaccine). The NCVIA also requires health care providers to report any adverse event that is listed in the VAERS Table of Reportable Events Following Vaccination if that event occurs within a specified time period after the child is vaccinated.

Health care providers are encouraged to report clinically significant adverse events that follow immunization to VAERS even if they are unsure whether the event was caused by vaccine.

There are three ways to report events to VAERS:

Submit an online form via a secure website at https://vaers.hhs.gov/esub/step1;
Fax a completed VAERS form to 877-721-0366; or
Mail a completed VAERS form to VAERS, P.O. Box 1100, Rockville, MD 20849-1100.

A VAERS form may be downloaded from the VAERS website at http://vaers.hhs.gov/resources/vaers_form.pdf. A VAERS form may also be requested by sending an e-mail to info@vaers.org, by calling toll-free 800-822-7967, or by sending a faxed request to 877-721-0366. For additional information on VAERS or vaccine safety, visit the VAERS website at www.vaers.hhs.gov or call 800-822-7967.

Where can I learn more about febrile seizures?

To learn more about febrile seizures, visit the following sites:

The National Institutes of Health (NIH), National Institute of Neurological Disorders and Stroke Febrile Seizures Information Page
The American Academy of Pediatrics healthy children website, which offers additional information about febrile seizures.