Febrile Seizures Following Childhood Vaccinations, Including Influenza Vaccination

What are febrile seizures?

The word “febrile” refers to having a fever. A seizure is a convulsion or fit of uncontrolled body movements. A “febrile seizure” refers to a seizure/convulsion 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, influenza, or ear infection. 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 rare after vaccination. Importantly, getting sick with the flu also can cause febrile seizures.

Flu illness can cause high fever and febrile seizures in children. Flu vaccine can protect children against flu illness and its complications (2017 Recommended Immunizations for Children from Birth Through 6 Years Old [269 KB, 2 pages]).  Flu vaccine cannot cause the flu because of the way that it’s made. See Misconceptions about Seasonal Flu and Flu Vaccines for more information.

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).
• Seasonal flu vaccine and the 2009 H1N1 flu vaccine were not found to be associated with febrile seizures in children during the 2009-10 flu season (Lee et al, 2011).
• Some studies have detected a small increased risk of febrile seizures in young children following the flu shot in some flu seasons. In these studies, the risk of febrile seizures was increased for children 12 through 23 months of age, particularly when the flu shot was given at the same time as pneumococcal conjugate vaccine (PCV13) (Tse et al, 2012) and diphtheria, tetanus, and pertussis (DTaP)-containing vaccine (Duffy et al, 2016).

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 eight integrated health care organizations which conducts ongoing vaccine safety monitoring and in depth analysis of vaccine safety 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 CDC via the Vaccine Adverse Event Reporting System (VAERS). Your doctor might file this report, or you can do it yourself through the VAERS website.

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 Febrile Seizure Page

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