Approximately 75 cases of encephalomyelitis which followed vaccination against smallpox have been reported in the United States, with a mortality of about 40 per cent. The disease has generally followed a primary inoculation, although in two reported instances it has occurred after a second.1 In the majority of cases in which encephalomyelitis has developed, vaccination has been performed on patients of school age. In an instance reported in the Netherlands,2 a 13 year old child died four days after vaccination. At the time of death there was no "take" at the site of vaccination; however, autopsy revealed the presence of lesions of the central nervous system similar to those of postvaccinal encephalitis.
The incubation period of postvaccinal encephalomyelitis ranges from seven to twelve days, and the disease is ushered in with acute manifestations. Characteristically there are headache, vomiting, drowsiness, fever, stiffness of the neck and paralysis. Zappert3
LAMM SS. POSTVACCINAL ENCEPHALOMYELITIS. Am J Dis Child. 1938;56(4):824-830. doi:10.1001/archpedi.1938.01980160104011