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Febrile Seizures Following Childhood Vaccinations, Including Influenza Vaccination

Questions & Answers

What are febrile seizures?

Febrile means “having a fever”. A seizure is a convulsion or fit of uncontrolled body movements. A “febrile seizure” refers to a seizure/convulsion that is associated with a fever in a child. Febrile seizures usually last around one or two minutes and can occur with any illness that causes fever, such as colds, flu, ear infection, or roseola. They are most common with fevers of 102°F (38.9°C) or higher, but they can also happen at lower body temperatures or when a fever is going down. A person experiencing a febrile seizure may lose consciousness.

Who is likely to have febrile seizures?

Most febrile seizures happen in children between the ages of 6 months and 5 years. Up to 5% of young children will have at least one febrile seizure. The most common age range for children to have febrile seizures is 14–18 months.

About 1 in 3 children who have one febrile seizure will have more febrile seizures during childhood. 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 are febrile seizures?

Febrile seizures can be frightening, but nearly all children who have a febrile seizure recover quickly, are healthy afterwards, and do not have any permanent neurological damage. Febrile seizures do not make children more likely to develop epilepsy or any other seizure disorder.

Can flu vaccines cause febrile seizures in children?

Vaccines can cause fevers, but febrile seizures are relatively rare after vaccination. Getting children the flu vaccine at the recommended time can prevent flu illness, which can cause high fever and febrile seizures.

Several studies of children in the United States have been conducted to see if there is an increased risk for febrile seizures following flu vaccination.

  • Flu vaccine was not found to be associated with febrile seizures in one study that looked at 45,000 children aged 6 months through 23 months of age who received a flu vaccine from 1991 through 2003 (Hambidge et al, 2006).
  • Flu vaccine and the 2009 H1N1 flu vaccine was not found to be associated with febrile seizures in children during the 2009-10 flu season (Lee et al, 2011).
  • Studies have detected a small increased risk of febrile seizures in young children following the flu shot in some flu seasons. The risk of febrile seizures has been highest in children 12-23 months of age and highest when the flu shot is given together with Pneumococcal conjugate vaccine (PCV13) (Tse el al, 2012).

The CDC carefully reviewed the data on febrile seizures and considered the benefits of vaccinating children against these illnesses, and decided that no changes in the childhood immunization recommendations should be made.

How does CDC monitor the safety of vaccines?

CDC and the Food and Drug Administration (FDA) closely monitor the safety of vaccines approved for use in the United States. CDC uses two primary systems to monitor the safety of flu vaccines:

  1. Vaccine Adverse Event Reporting System (VAERS): an early warning system that helps CDC and FDA monitor problems following vaccination. Anyone can report possible vaccine side effects to VAERS. Generally, VAERS reports cannot determine if an adverse event was caused by a vaccine, but these reports can help determine if further investigations are needed.
  2. Vaccine Safety Datalink (VSD): A collaboration between CDC and nine health care organizations which allows ongoing monitoring and proactive searches of vaccine-related data.

Learn more about vaccine safety monitoring at Vaccine Safety Monitoring at CDC.

Can febrile seizures after a childhood vaccination be reported to CDC?

Yes. Febrile seizures following vaccination can be reported to the Vaccine Adverse Event Reporting System (VAERS). Your doctor might file this report, or you can do it yourself through the VAERS website, or by calling 1-800-822-7967.

Where can I learn more about febrile seizures?

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

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