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Children's Vaccines Health Center

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Combo Vaccine Raises Risk of Seizures in Toddlers?

Safer to give MMR and chickenpox shots separately for first dose, researchers say


Overall, the study found, children's seizure rate peaked seven to 10 days after they were vaccinated. At that point, there were almost six seizures for every 10,000 doses of the MMRV, versus two seizures for every 10,000 doses of the separate vaccines.

"You see the same increase in risk with these different formulations," said MacDonald, referring to the Priorix-Tetra and ProQuad vaccines.

The traditional approach -- separate MMR and chickenpox vaccines -- seems safer.

"There's no question children should be vaccinated," MacDonald said.

As of May 30, the U.S. Centers for Disease Control and Prevention had received reports of 334 measles cases in 18 states. Nearly all have involved unvaccinated U.S. residents who traveled to countries where measles is common, then brought the virus home with them.

Besides causing misery -- fever, cough, and a body-wide rash -- measles infection can lead to serious complications. Up to 5 percent of infected children develop pneumonia, the CDC says, while one in 1,000 suffers brain inflammation. And for every 1,000 children who develop measles, one or two will die.

But parents should be aware that the MMRV carries a higher seizure risk and discuss that with their pediatrician, MacDonald said. Some parents may still want the combined shot, to spare their child from two needle jabs, she added.

Based on the ProQuad study, the U.S. Advisory Committee on Immunization Practices changed its stance on the MMRV. Now it says that unless parents ask about the combined vaccine, doctors should default to separate shots for young children getting their first dose of the MMR and chickenpox vaccines.

The story is different, though, with the second dose, typically given between the ages of 4 and 6 years. In general, fever-related seizure is uncommon at those ages, and the advisory committee says the MMRV is the better option.

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