The most feared complications are CNS complications, such as encephalitis and encephalopathy [69] , which occur in 1 in 100,000 to 500,000 [67] . Postvaccinal encephalitis presents with headache, meningismus, fever, drowsiness, and vomiting; some cases are accompanied by spastic paralysis. A second form, postvaccinal encephalomyelitis, may present in 11 to 15 days after vaccination, similar to encephalitis with fever, mental status change, meningeal signs, seizures, and additional spinal cord dysfunction. Mortality of these complications is as high as 25% [62] , and 25% of survivors develop persistent deficits [67] .