Epilepsy can be caused by vaccination as a leading symptom of vaccine-induced encephalopathy and febrile seizures can also occur as a result of vaccine-induced fever. Pertussis vaccination is a highly effective means to prevent a disabling and sometimes deadly disease. The live vaccines and the vaccines prepared from infective neural tissue are perhaps the vaccines that carry the greatest risk. The cellular vaccines, and also vaccines with high levels of endotoxin, are said to be generally less safe than the acellular vaccines although evidence on these points is weak especially where seizures are a rare side effect, largely because of the absence of sufficiently powered comparisons. The risks also probably vary according to manufacturer and to the quantity and type of adjuvant which further complicates assessment. Case reports exist of epilepsy, autism, and cerebral palsy developing after measles, mumps, rubella (MMR) and measles vaccines.