A seizure is a sudden, uncontrolled electrical disturbance in the brain that causes a jerking or staring spell. Seizures are also known as convulsions. A common cause of seizures in young children and infants is fever. If a child has a febrile seizure after being vaccinated, keep mind that the fever, not the vaccine, causes the seizure. While these can be frightening for parents, these types of seizures are usually not harmful. While children will outgrow febrile seizures, Epilepsy is a chronic seizure disorder that can affect people for life.