Study: Fever-associated seizures after vaccination do not affect development, behavior

A seizure associated with a fever is called a febrile seizure. Now a new study has found there is no difference in developmental and behavioral outcomes for children who have febrile seizures after vaccination, children who have febrile seizures not associated with vaccination and children who have never had a seizure. The new study is published in the July 1, 2020 online issue of Neurology, the medical journal of the American Academy of Neurology. Febrile seizures are also known as febrile convulsions.

"This is reassuring news for parents," said study author Lucy Deng, MBBS, of the National Centre for Immunisation Research and Surveillance (NCIRS) in Sydney, Australia. "A febrile seizure can occur following vaccination and understandably can be quite distressing to parents. It can also cause parents to lose confidence in future vaccinations. Now, parents will be relieved to hear that having a febrile seizure following vaccination does not affect the child's development."

The study compared 62 children who had a fever-associated seizure within two weeks after a vaccination with 70 children who had a fever-associated seizure from another cause and 90 children without a history of seizures. All of the children who had seizures were younger than 2-1/2 years old at the time of the seizure.

The children's cognitive, motor and language functions were tested by certified developmental assessors who did not know the child's seizure history. Their behavior was also assessed through questionnaires completed by their parents. The children with seizures were tested within one to two years after the seizure.

The researchers found no differences in development, thinking skills or behavior between the children who had febrile seizures following a vaccination and those who had febrile seizures at other times or those who never had a seizure.

"At a time when there is a global resurgence of measles and new diseases are emerging, our findings are particularly important in reassuring parents and providers on the safety of vaccines," Deng said.

Deng also pointed out that several other factors were not associated with having developmental problems: fever-associated seizures before the age of one; a febrile seizure lasting for more than 15 minutes; or more fever-associated seizures after the first seizure.

Limitations of the study include a relatively small number of participants. Also, further studies should follow children for longer periods of time.