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New research reassures parents that febrile seizures following vaccination not dangerous

New research from The University of Sydney and the National Centre for Immunisation Research and Surveillance (NCIRS) has found the severity of febrile seizures following vaccination is no different from the severity of febrile seizures due to another cause, and that the majority of seizures are short-lived, self-resolving and don’t require ongoing treatment.

Children living in Australia would have received 13 vaccinations by the time they reach two years of age. Reassuringly, febrile seizures following vaccination accounted only for 6 per cent of all first febrile seizure presentations to Australian children’s hospitals.

Febrile seizures are the most common type of childhood seizures, affecting approximately 1 in 30 children under six years of age. They are triggered by a sudden rise in body temperature and are often associated with a febrile viral illness such as influenza. Febrile seizures are generally short and don’t require ongoing treatment. Children can get a fever following a vaccination, which can also result in a febrile seizure.

Published last week in Pediatrics, this is the first prospective study to directly compare the differences in severity and outcomes between febrile seizures following vaccination and other febrile seizures.

“Febrile seizures are not known to cause long-lasting effects, but they are understandably frightening to parents and carers,” said Dr Lucy Deng, lead author and PhD student from The University of Sydney and NCIRS.

“In our study of 1,022 children with their first febrile seizure, we found no difference between febrile seizures following vaccination and other febrile seizures with regard to the length of the seizure, the risk of having another febrile seizure in the first 24 hours, the length of hospital stay or the need for seizure medication on discharge.”

“It is known that some vaccines are associated with an increased rate of febrile seizure at a time when there is a fever peak after vaccination, for example, 5 to 12 days after a measles-containing vaccine or in the first 2 days after some influenza vaccines when given together with pneumococcal vaccines.”

Senior author Associate Professor Nicholas Wood from The University of Sydney and NCIRS said: “We hope this gives parents the confidence to continue vaccinating their children, especially now at a time when there have been cases of both measles and whooping cough and we prepare to enter into the flu season.”

“In addition to not finding any difference in the severity of seizures, we found 12 per cent of children with febrile seizures following vaccination had an infection found on laboratory testing. That is, these children also had a respiratory infection, urinary tract infection or gastroenteritis that may have contributed to the febrile seizure. These children who had both infection and recent vaccination were more likely to stay in hospital for longer compared to those who weren’t found to have an infection.”

The study

The study compared febrile seizures following vaccination to febrile seizures unrelated to vaccination, looking specifically at the length of the seizure, recurrence of seizure, need for intensive care unit admission, length of hospital stay and use of seizure medication. Researchers collected information on all children who presented to the emergency department at five paediatric hospitals across Australia over a 14-month period through the Paediatric Active Enhanced Disease Surveillance (PAEDS) network. This study was conceived and led by Associate Professor Nicholas Wood who identified a lack of information on the clinical characteristics of febrile seizures following vaccinations.

doi: 10.1542/peds.2018-2120