It is estimated that the childhood lifetime risk of a febrile seizure is 2-4%. With each seizure there is a concern for neurological damage and the development of future problems including epilepsy and neuropsychiatric syndromes including autism spectrum disorder. Nilsson et al, examined a sample of adults with children who had well-documented febrile seizures earlier in life. An astounding 41% had early symptomatic neurodevelopmental symptoms eliciting clinical evaluation (ESSENCE). ESSENCE, in this context, refers to the total group of neurodevelopmental/neuropsychiatric disorders: Attention-deficit/hyperactivity disorder, Autism Spectrum Disorder, Developmental Coordination Disorder, Intellectual Disability, Developmental Language Disorder, and Tourette syndrome—all characterized by major cognitive and/or behavioral problems.
Duffy et al from the CDC used the Vaccine Data Safety Link to study febrile seizures in children ages 1 to 5 months of age after vaccination. They used extensive methods to exclude cases and report on 15 where it was absolutely certain that combination vaccination caused the seizure.
Hellbound and Down 