CDC Recommends Splitting 1st Doses of MMR and Chickenpox Vaccines

On the heels of two studies suggesting a combination vaccine against measles, mumps, rubella and chickenpox doubles a child’s risk for febrile seizure, the U.S. Centers for Disease Control (CDC) recommended May 7 that children have their first dose of these vaccines as two separate shots – one against measles, mumps and rubella (MMR) and the other against varicella (chickenpox). The combo vaccine, brand name ProQuad, was first licensed in 2005 but didn’t become widely available in the U.S. until 2009.


Febrile seizures are convulsions brought on by fever, and usually happen in children 6 months to 5 years old. About one in every 25 children will have a febrile seizure, and while they can be terrifying for parents, the majority of these are harmless. And even with the combination vaccine, incidence of febrile seizures is small. About two of every 2,500 who receive the MMRV vaccine have febrile seizures, compared with one of every 2,500 who have MMR and a separate shot for varicella.

Most kids receive their first doses of these vaccines when they are 12-15 months old, with a booster shot at age 5 or 6. The CDC still recommends the combination vaccine (MMRV) for this booster as long as the child has no family or personal history of seizures.

Read the CDC recommendation

Learn more about febrile seizures

Related information

Some Parents Worry About Side Effects, But Most Still Vaccinate

How to Ask Questions about Vaccines without Getting Kicked Out of Your Doctor’s Office

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