CDC Warns Vaccines May Cause Seizures
Frequently Asked Questions about Febrile Seizures Following Childhood Vaccinations
CDC and the Food and Drug Administration (FDA) continually monitor the safety of recommended vaccines. This includes looking to see whether, and how frequently, vaccines are associated with fever-related (febrile) seizures. CDC’s Advisory Committee on Immunization Practices (ACIP) is reviewing vaccine safety data on febrile seizures in the United States following 2010-11 inactivated influenza (flu) vaccination. Monitoring that’s been done for the 2010-11 flu season suggests that when flu vaccine and 13-valent pneumococcal conjugate vaccine (PCV 13) are given on the same day, there may be an association with febrile seizures in children aged 12 to 23 months. To date, this association of febrile seizures to flu vaccine is much lower than the association observed particularly during 2010 in the Southern Hemisphere and similar to what is observed with other U.S.-licensed childhood vaccines.
This page addresses questions about febrile seizures following childhood immunizations. For more information on multiple immunizations given during childhood, read Frequently Asked Questions about Multiple Vaccinations and the Immune System.
"Febrile" means "relating to a fever." In some children, having a fever can bring on a 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. They are most common with fevers reaching 102°F (38.9°C) or higher but can also occur at lower temperatures or when a fever is going back down.
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.
Febrile seizures can occur when a child has a fever from any cause. They are most common after infections, including those that can be prevented by vaccination. But in rare instances, febrile seizures can occur after vaccination.
Studies have shown that there is a small increased risk for febrile seizures during the first to second week after vaccination with measles, mumps, rubella (MMR) vaccine and the first dose of measles, mumps, rubella, and varicella (MMRV) vaccine. DTP (whole cell pertussis) vaccine is no longer used in the United States, but when it was in use there was also a small increased risk for febrile seizures after DTP on the day the vaccine was given. Studies have not shown an increased risk for febrile seizures after the acellular pertussis vaccine, DTaP, or after varicella (chickenpox) vaccine.
Several studies of children in the United States in previous influenza seasons 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.
Systems are in place to monitor adverse events, including seizures, after seasonal flu vaccines. During the 2010-11 influenza season, FDA and CDC have detected a small increase in the number of reports to the Vaccine Adverse Event Reporting System (VAERS) of febrile seizures following vaccination with trivalent inactivated influenza vaccine (TIV) primarily in children younger than 2 years of age. Monitoring to date has shown that when flu vaccine and 13-valent pneumococcal conjugate vaccine (PCV 13) are given on the same day, there may be an association with febrile seizures in children aged 12 to 23 months. However, based on available data, this association appears to be similar to the small increased risk of having a febrile seizure after MMRV compared with MMR and varicella given separately. Recommendations for the use of the 2010-11 flu vaccine in children have not changed. CDC recommends that all persons ages 6 months and older receive a flu vaccine each year.
Febrile seizures are not uncommon. About 2%-5% of young children will have at least one febrile seizure. Most febrile seizures occur in children between the ages of 6 months and 5 years. The peak age is 14–18 months, which overlaps with the ages when first doses of the MMRV, MMR, and varicella vaccines are recommended. 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.
Most 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. Most children (greater than 90%) who have a seizure will not develop epilepsy. Genetic predisposition 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.
Two studies have shown that children who have febrile seizures after receiving an MMR vaccine are no more likely to have epilepsy or learning or developmental problems than children who have febrile seizures that are not associated with a vaccine. Experts believe it is likely that this finding for MMR vaccine applies to MMRV vaccine as well.
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.
The National Childhood Vaccine Injury Act (NCVIA) requires healthcare 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 healthcare providers to report any adverse event that is listed in the Vaccine Adverse Event Reporting System (VAERS) Table of Reportable Events Following Vaccination [PDF - 34 KB] if that event occurs within a specified time period after the child is vaccinated.
Healthcare providers are encouraged to report other 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 web site;
- 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 [PDF - 2 Pages] from the VAERS web site. A VAERS form may also be requested by sending an e-mail to firstname.lastname@example.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 web site 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 StrokeFebrile Seizures Information Page
- The American Academy of Pediatrics healthy children web site, which offers additional information about febrile seizures.