Authors’ conclusions: among 12-23-month-olds receiving their first dose of Measles-Mumps-Rubella (MMR) vaccine, the risk of fever and febrile seizures are elevated 7 to 10 days after vaccination. This already known risk increases with the Measles-Mumps-Rubella-Varicella (MMRV) vaccine, resulting in 1 additional febrile seizure for every 2,300 doses of this vaccine.
Reviewers’ commentary: this study, involving nearly half a million children, provides results that confirm prelicensure safety data about the increasing risk of febrile seizures 7 to 10 days after vaccination with the new MMRV vaccine, compared to separate MMR and Varicella vaccines. This risk is estimated to be 1 per 2,300 doses of the new vaccine. Paediatricians should be aware of this risk when recommending or not recommending this vaccine.