Higher MMRV seizure risk not alarming

Doctors are being reassured about the safety of the combined measles, mumps, rubella and varicella vaccine, after research found it was associated with a risk of febrile seizures. 

Children given the MMRV shot had double the rate of febrile seizures 7-10 days after vaccination, compared with those who received the varicella and MMR vaccine separately, an analysis of more than 227,000 Canadian children found.

But at about one excess seizure for every 2841 doses, the absolute risk was small, the researchers wrote in the CMAJ. Lead author Dr Shannon MacDonald urged doctors not to be dissuaded from administering MMRV, saying the benefits outweighed the risks.

“Combining MMR and varicella into a single vaccine decreases pain for children and distress for parents, thus addressing common barriers to vaccine uptake, and may improve vaccination coverage levels and decrease immunisation delivery costs,” she said.

Since July 2013, Australia’s National Immunisation Program has included an MMRV vaccination for 18-month-olds.

Associate Professor Kristine Macartney said the program was specifically designed to reduce the risk of fever and febrile seizures, which is only significant following the first dose of either MMR or varicella vaccine.

“The heightened risk of fever in the combination vaccine isn’t apparent when given as the second dose,” said Professor Macartney, from the National Centre for Immunisation Research and Surveillance.

“So we think there will be less of a chance we’ll see seizures at the second dose, but we’re on the lookout.”

Professor Macartney and her colleagues are conducting surveillance at five major hospitals across Australia to monitor for seizures after the second dose.

CMAJ 2014; online.