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Questions and Answers about MMRV Safety Monitoring of Febrile Seizures

This page addresses questions related to CDC study on the combined measles, mumps, rubella, and varicella (MMRV) vaccine and febrile seizures.

What is ProQuad?
ProQuad® is the trade name for a vaccine made up of measles, mumps, rubella, and varicella (chickenpox) components (MMRV). It was licensed in 2005 for use among children ages 12 months to 12 years. It is a single shot that can be used in place of two other shots—the measles, mumps, and rubella (MMR) vaccine and the varicella vaccine. Using it lowers the number of shots a child needs to receive to be protected from these 4 diseases.

Is the MMRV vaccine available in the United States?
Very little MMRV vaccine is available in the United States due to manufacturing issues unrelated to vaccine safety. MMRV vaccine is not expected to be available again until 2009. However, some clinics may have some MMRV vaccine in stock.

What adverse events were reported among children following MMRV vaccination before the vaccine was licensed?
Mild adverse events have been found, including—

  • Soreness or swelling where the shot was given (about 1 child out of 5)
  • Fever (about 1 child out of 5)
  • Rash (about 1 child out of 20)

The MMRV vaccine, compared with MMR and varicella vaccines given separately, has been associated with higher rates of fever and a measles-like rash during the 5–12 days after vaccination.

What is a febrile seizure?
"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 that go up fast and reach 102°F (38.9°C) or higher, but can also occur when a fever is going back down. Febrile seizures may happen with any condition that causes a fever, including common childhood illnesses like ear infections and, rarely, vaccination.

Who is at risk for febrile seizures?
Most febrile seizures occur in children between the ages of 6 months and 5 years. The peak age is 14 to 18 months, which overlaps with the ages when first doses of the MMRV, MMR, and varicella vaccines are recommended. If a member of a child's immediate family has had febrile seizures, that child is more likely to have a febrile seizure.

Are children more likely to have a febrile seizure after getting the MMRV vaccine than after getting MMR and varicella (chickenpox) vaccines?
Early findings from an ongoing CDC study show that children who get an MMRV vaccine may be twice as likely to have a febrile seizure 7–10 days after getting the shot than children who get MMR and varicella vaccines (2 shots) at the same health care visit.

During the 7–10 days after vaccination, about one additional febrile seizure would be expected to occur among every 2,000 children vaccinated with MMRV vaccine, compared with children vaccinated with MMR and varicella vaccine administered at the same visit.

Is the study completed?
No. This study shows early results only. CDC and the Food and Drug Administration will continue to assess this information. Continue to visit this page for updated information.

Does the MMR vaccine cause febrile seizures?
Children who receive the MMR vaccine are more likely to have febrile seizures 8–14 days after vaccination than children who are not vaccinated at all.1 During the 8–10 days after vaccination, about one additional febrile seizure occurs among every 3,000–4,000 children who receive MMR vaccine, compared with children who do not receive any vaccines.

Does a varicella vaccine cause febrile seizures?
Varicella vaccine is not known to cause febrile seizures. A study among nearly 90,000 children who received varicella vaccine showed no increased risk of febrile seizures due to varicella vaccine.

How serious is a febrile seizure?
Although febrile seizures can be frightening for the child’s caregivers, most are harmless. The majority of children who have febrile seizures recover quickly and have no lasting effects. Up to half of children who have one febrile seizure will have at least one other febrile seizure. But children with simple febrile seizures—the most common form—have no greater chance of getting epilepsy or brain damage than children who do not have febrile seizures. A study1 showed that children who have febrile seizures after receiving an MMR vaccine are no more likely to have more seizures, epilepsy, or learning or developmental problems than children who have febrile seizures that are not associated with a vaccine.

Can febrile seizures after vaccination 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.

1 Barlow WE, Davis RL, Glasser JW, Rhodes PH, Thompson RS, Mullooly JP, Black SB, Shinefield HR, Ward JI, Marcy SM, DeStefano F, Immanuel V, Pearson JA, Vadheim CM, Rebolledo V, Christakis D, Benson PJ, Lewis N, Chen RT, for the Centers for Disease Control and Prevention Vaccine Safety Datalink Working Group. The risk of seizures after receipt of whole-cell pertussis or measles, mumps, and rubella vaccine.* The New England Journal of Medicine 2001;345(9):656–661.

Additional Resources

For more information about this study, please visit:

PDF IconPlease note: Some of these publications are available for download only as Portable Document Format (PDF) files, which require Adobe® Acrobat® Reader to view. Please review the information on downloading and using Acrobat Reader software.

*Links to non-Federal organizations found at this site are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization Web pages found at these links.

Page last reviewed: June 23, 2008
Page last updated: March 17, 2008
Content source: Immunization Safety Office

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