Definition:
Post-vaccinial encephalitis is an inflammation of the brain or central nervous system most likely caused by an autoimmune or allergic reaction, not the direct infection of the central nervous system with the vaccinia virus. The symptoms are fever, headaches, stiff neck, light-sensitivity, and coma, which develop 8 to 15 days after vaccination. Prior to 1960, this complication was reported to occur in 3 to 12 people per million people vaccinated. About 15-25% of people who develop this complication die, and 25% develop some type of permanent brain damage. There is no treatment for post-vaccinial encephalitis. Vaccinia immune globulin (VIG) is not effective.
