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What Parents Need to Know About MMRV Vaccine and Fever-Related Seizures

Since 1972, the measles, mumps, rubella (MMR) vaccine has played a major role in ending the transmission of measles and rubella in the United States. In 2005, the U.S. Food and Drug Administration (FDA) licensed the combination measles, mumps, rubella, and varicella virus vaccine live (MMRV or ProQuad ®) for use in children 12 months to 12 years of age. The MMRV combination vaccine was designed to reduce the number of shots a child receives for MMR and varicella (chickenpox).

Scientific Review


As part of routine safety monitoring for new vaccines, in 2007, the Centers for Disease Control and Prevention (CDC) and Vaccine Safety Datalink (VSD) scientists began a study to monitor adverse events related to MMRV. The study assessed the risk of febrile (fever-related) seizures in children aged 12 to 23 months who received MMRV, compared with children who received MMR and varicella separately at the same visit.

First dose in infants. Investigators reviewed the medical history for 96 of the 118 infants aged 12 to 23 months who reported seizures after vaccination. The data suggest that about one more fever-related seizure is expected for every 2,000 infants vaccinated with MMRV, as compared to separate, simultaneous MMR and varicella vaccines.

Second dose in children. A second vaccine does is recommended at 4 to 6 years of age. At this age, we do not have enough data to know whether the risk of fever-related seizures is higher in children who receive an MMRV vaccine compared with MMR and varicella vaccines given separately at the same visit.

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Please Note

Fewer 4 to 6 year-old children have fever-related seizures than 12 to 23 month-old infants.

Next Steps


To ensure the safety of MMRV, CDC and FDA investigators will--

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What Parents Should Do


  • Parents should discuss their child's unique medical profile with health care providers to determine if he or she may have an increased risk for fever-related seizures.
  • Parents should monitor their child for a high fever for 10 days after vaccination with MMRV.
  • If your child experiences a fever after vaccination, give your child an aspirin-free pain reliever immediately.

Please Note

Fever-related seizures generally have an excellent outcome. Most fever related seizures occur in young children between the ages of 6 and 59 months. The peak age is 14 to 18 months, the age when the first dose of MMRV or MMR and varicella vaccines are recommended. Studies have not shown any long-term risks in children who had fever-related seizures following an MMR vaccine.

Most children who receive the MMRV vaccine do not have any problems. However, any vaccine, like any other medicine, can cause serious health problems such as severe allergic reactions. Being vaccinated with an MMRV vaccine is much safer than getting measles, mumps, rubella, or chickenpox.

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Additional Resources


For more information about this study, please visit:

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

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