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Children's Vaccines Health Center

Seizure Risk Rises With MMRV Vaccine

Febrile Seizures Nearly Double With Measles-Mumps-Rubella-Chickenpox Vaccine, but Risk Still Slight, Study Says
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Vaccines and Seizures Data

In the newly published report, Klein and her team looked at reports of seizures and fevers among more than 376,000 infants given the vaccines in two injections and more than 83,000 given the four-in-one.

Seizures and fever clustered around 7 to 10 days after all measles vaccines, but the risk during that time was higher for the four-in-one than for the two injections.

"There is a doubling of risk with MMRV, but it's [still] slight," she tells WebMD. "There is a low risk overall."

About Febrile Seizures

About one in 25 infants has one or more febrile seizures, defined as convulsions brought on by high fever, says Randy Bergen, MD, a pediatric infectious disease specialist at Kaiser Permanente in Walnut Creek, Calif.

"They are very scary to observe," he says. Most last only 30 seconds to 2 minutes or so, he says. The child may stiffen and roll his eyes. "From a medical point of view, febrile seizures are not in any way considered dangerous," Bergen says. Children who have the seizures don't have a greater chance of getting epilepsy or brain damage.

Comparing Vaccines: Second Opinion

''This is a confirmatory study, this is not new information," says John Bradley, MD, a member of the American Academy of Pediatrics' Committee on Infectious Diseases and director of the Division of Infectious Diseases, Rady Children's Hospital of San Diego, who reviewed the study for WebMD.

"For probably two years we have been aware that if you give MMRV you get a higher fever and more febrile seizures than if you give them separately," he says.

Still, the information is important for parents to know, he says, even though the increased risk with the 4-in-1 is slight compared to giving MMR and varicella separately.

Bradley says the information only applies to the first dose of vaccine, not the second, given around kindergarten age. "This phenomenon of febrile seizures only occurs in the infants," he says, because of brain immaturity. Peak age is 14 to 18 months, according to the CDC, and that overlaps with when the first doses of measles and chickenpox vaccines are recommended.

The stance of the AAP committee, Bradley says, is that both vaccines are acceptable but that parents need the information about seizure risks to make an informed decision, weighing the lower seizure risk with the need for another injection for the first dose. (The combination is generally preferred for the second dose, according to the ACIP guidelines.)

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