Combination MMRV Doubles Risk of Febrile Seizure


Did the title get your attention? It was meant to, but now let me remove your alarm. Even though this new study from the Kaiser Permanente Vaccine Study Center showed that infants receiving their first dose of the MMRV have a two-fold increased risk of fever and febrile seizures after vaccination compared with same-day administration of a separate shot for MMR (measles, mumps and rubella) and the varicella (chickenpox) vaccine, the risk of having a febrile seizure after the vaccination remains very small.

The risk of febrile seizures from either [vaccine] is less than 1 in 1,000. A febrile seizure is a brief, fever-related convulsion but it does not lead to epilepsy or seizure disorders. Febrile seizures are far more likely to be caused by a cold or virus than a vaccine.

Vaccinations have done much to reduce the occurrence of childhood diseases and the risks of complications that can occur from them. Vaccinations are not without risks, but these occur much less often than the ones associated with the diseases they prevent.

Nicola Klein, MD, Ph.D., co-director of the Kaiser Permanente Vaccine Study Center, and colleagues study appears online in the journal Pediatrics today. The study was funded by the Centers for Disease Control and Prevention looking for the safest way to give infants and children vaccinations.


The study analyzed 459,000 children 12 to 23 months old using electronic health records (EHRs) from systems across the United States who received their first dose of measles-containing vaccine. The researches found MMRV to be associated with a two-fold increased risk of fever and febrile seizures 7-10 days after vaccination compared with same-day administration of a separate shot for MMR and the varicella (chickenpox) vaccine.

It is important to note that the absolute number of febrile seizures were small: The combo vaccine produced just one additional fever-related seizure for every 2,300 doses. The window of risk was between seven and 10 days post-vaccination.

The CDC, using this data, has already recommended that either form of the vaccine is fine for one- to two-year-olds, but that if parents have no preference pediatricians should give the MMR and varicella (chicken pox) shots separately during the same visit.

This isn’t the same as further breaking the MMR into separate vaccines, which the CDC recommends against.

The four-in-one MMRV vaccine, called ProQuad, is made by Merck. MMRV was licensed by the FDA in 2005 and was subsequently recommended by the Advisory Committee on Immunization Practices (ACIP) in 2006.