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Febrile seizure rate higher with MMRV vaccine than with MMR + V

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – The quadrivalent measles-mumps-rubella-varicella vaccine is associated with twice as many febrile seizures as same-day vaccination with separate MMR and varicella vaccines, according to a report in the July issue of Pediatrics.

Still, the authors emphasize that the absolute is very low, and that febrile seizures per se are benign.

Lead author Dr. Nicola P. Klein, at the Kaiser Permanente Vaccine Study Center in Oakland, California, and colleagues first identified an increased risk of febrile seizures with the combination MMRV vaccine 2 years ago, and now they repot updated data. “The aim of our study was to compare MMRV with same-day administration of MMR + V vaccines, both of which are currently recommended vaccines for 1-2 year olds,” Dr. Klein noted in comments emailed to Reuters Health.

Over 63,000 recipients of the MMRV vaccine were compared with more than 376,000 children given MMR + V. During days 7-10 days after vaccination, when febrile seizures clustered significantly, there were 77 such cases in the former group and 174 in the latter — yielding a relative risk of 1.98 for MMRV.

“Pediatricians recommending MMRV for their 1-2 year old patients should communicate to parents that it increases the risk of fever and febrile seizure 7-10 days after vaccination over that already associated with measles-containing vaccines,” Dr. Klein advised.

The absolute risk is still low, the investigators note. “Vaccination with MMRV results in 1 additional febrile seizure for every 2300 doses given instead of separate MMR + varicella vaccines.”

Still, they recognize that parents are likely to be concerned, and Dr. Klein suggested how pediatricians can address those concerns by putting the risk in perspective. “The risk for febrile seizures after any measles-containing vaccine (MMR and MMRV) is low, less than 1 febrile seizure per 1000 vaccines. Febrile seizures are very common and are much more commonly associated with colds and other infections than they are with immunization. While they are frightening for the parents, febrile seizures are benign and do not lead to epilepsy or seizure disorders.”

The authors note that the Centers for Disease Control and Prevention recently recommended that if parents don’t have a strong preference for MMRV vaccine, children should receive the MMR + varicella vaccines — although either vaccine may be used

Reference:

Pediatrics 2010; 126:e1–e8.