The Smallpox Vaccine and Postvaccinal Encephalitis

Semin Neurol. 2002 Mar;22(1):95-8. doi: 10.1055/s-2002-33052.


Smallpox is one of the deadliest infectious diseases in history. The discovery by Edward Jenner that inoculation with a droplet of pus from a cow with cowpox protected a person from smallpox resulted in the successful vaccination of millions of people. There were, however, complications associated with smallpox vaccination; the most serious complication was postvaccinal encephalitis, which was reported to occur with an incidence of 1 in 110,000 vaccinations and a case-fatality rate of 50%. Before we become complacent with the idea that we will respond to a bioterrorism attack with a mass immunization program for smallpox, it is important to be reminded of the risk and clinical manifestations of postvaccinal encephalitis and the efficacy of antivaccinia gamma-globulin in preventing this complication. The first case of postvaccinal encephalitis as a complication of the Jennerian cowpox inoculation was observed in 1905. A century later, there is no effective therapy.

Publication types

  • Historical Article

MeSH terms

  • Animals
  • Antibodies, Viral / therapeutic use
  • Antiviral Agents / therapeutic use
  • Bioterrorism*
  • Cidofovir
  • Contraindications
  • Cytosine / analogs & derivatives
  • Cytosine / therapeutic use
  • Encephalomyelitis, Acute Disseminated / etiology
  • Encephalomyelitis, Acute Disseminated / history*
  • Encephalomyelitis, Acute Disseminated / prevention & control
  • Female
  • History, 19th Century
  • History, 20th Century
  • Humans
  • Male
  • Organophosphonates*
  • Organophosphorus Compounds / therapeutic use
  • Smallpox / mortality
  • Smallpox / prevention & control
  • Smallpox / transmission
  • Smallpox Vaccine / adverse effects*
  • Smallpox Vaccine / history
  • Vaccination / adverse effects*
  • gamma-Globulins / therapeutic use


  • Antibodies, Viral
  • Antiviral Agents
  • Organophosphonates
  • Organophosphorus Compounds
  • Smallpox Vaccine
  • gamma-Globulins
  • Cytosine
  • Cidofovir