New research from the University of Sydney has found the severity of febrile seizures following vaccination is no different to febrile seizures from another cause, such as from a virus, and that the majority of seizures are short-lived, self-resolving and don’t require ongoing treatment.

While each Australian child would have received 13 vaccinations by the time they reach two years of age, febrile seizures following vaccination accounted only for 6 per cent of all first febrile seizure presentations to hospital.

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

Published today in Paediatrics, this is the first prospective study to directly compare the differences in severity and outcomes between febrile seizures following vaccination to 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 University of Sydney and the National Centre for Immunisation Research and Surveillance (NCIRS).

“In our study of 1022 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, five to 12 days after a measles-containing vaccine or in the first two days after some influenza vaccines when given together with pneumococcal vaccines.”

Senior author Associate Professor Nicholas Wood from 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 percent 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 that weren’t found to have an infection.”