Four young children, who were otherwise normal, developed an illness characterized by the sudden onset of an isolated, prolonged generalized seizure 7 to 8 days following smallpox vaccination. This convulsive episode was unlike that of a simple febrile convulsion, commonly seen in this age group. A rapid, complete recovery and an absence of further convulsive disorder were noted in all 4 children. The significance of this clinical picture is discussed, particularly in view of recent studies of the nervous system complications following smallpox vaccination.
Hoefnagel D. Acute, Transient Encephalopathy in Young Children Following Smallpox Vaccination. JAMA. 1962;180(7):525-527. doi:10.1001/jama.1962.03050200009003