Why Smallpox Bioterrorism?

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Why Smallpox Bioterrorism?

• Stable aerosol Virus
• Easy to Produce
• Infectious at low doses
• Human to human transmission
• 10 to 12 day incubation period
• High mortality rate (30)
• CDC Materials

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Small Pox Vaccine History

• 1000 AD - China, deliberate inoculation of
  smallpox into skin or nares resulting in less
  severe smallpox infection. Vaccinees could still
  transmit smallpox
• 1796 - Edward Jenner demonstrated that skin
  inoculation of cowpox virus provided protection
  against smallpox infection
• 1805 - Italy, first use of smallpox vaccine
  manufactured on calf flank
• 1864 - Widespread recognition of utility of calf
  flank smallpox vaccine
• 1940s - Development of commercial process for
  freeze-dried vaccine production (Collier)

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Herd Immunity

• Smallpox Spreads to the Non-immune
• Immunization Slows the Spread Dramatically
• Epidemics Die Out Naturally
• Herd Immunity Protects the Unimmunized

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Smallpox Vaccine

• Live Virus Vaccine (Vaccinia Virus)
• Not Cowpox, Might be Extinct Horsepox
• Must be Infected to be Immune
• Crude Preparation We Have Now
• Prepared from the skin of infected calves
• Filtered, Cleaned (some), and Freeze-dried
• New Vaccine is Clean, but still Live

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Complications of Vaccination

• Local Lesion
• Can be Spread on the Body and to Others
• Progressive (Disseminated) Vaccina
• Deadly Like Smallpox, but Less Contagious
• Encephalitis
• Heart Disease?

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Historic Probability of Injury

• Small Risk from Bacterial and Viral Contaminants
• Small Risk of Allergic Reaction
• 35 Years Ago
• 5.6M New and 8.6M Revaccinations a Year
• 9 deaths, 12 encephalitis/30-40 permanent
• Death or Severe Permanent Injury - 1/1,000,000
• Mostly among immunsupressed persons

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Global Eradication Program

• 1950 - Pan American Sanitary Organization
  initiated hemisphere-wide eradication program
• 1967 - Following USSR proposal (1958) WHO
  initiated Global Eradication Program
• Based on Ring Immunization
• Vaccinate All Contacts and their Contacts
• Isolate Contacts for Incubation Period
• Involuntary - Ignore Revisionist History
• 1977 - Oct. 26, 1977 last known naturally
  occurring smallpox case recorded in Somalia
• 1980 - WHO announced world-wide eradication

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Eradication Ended Vaccinations

• Cost Benefit Analysis
• Vaccine was Very Cheap
• Program Administration was Expensive
• Risks of Vaccine Were Seen as Outweighing
  Benefits
• Stopped in the 1970s
• Immunity Declines with Time

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Universal Vulnerability

• Agriculture and Smallpox
• Stays Endemic or Dies Out Forever
• Most Communities had Significant Immunity
• Isolated Communities
• Synchronous Infection
• Break Down of Social Order
• Now the Whole World is Susceptible

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How Have Risks Changed?

• Immunosuppressed Persons Cannot Fight the Virus
  and Develop Progressive Vaccinia
• Immunosuppression Was Rare in 1970
• Immunosuppression is More Common
• HIV, Cancer Chemotherapy, Arthritis Drugs, Organ
  Transplants

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Role of Medical Care

• Smallpox
• Can Reduce Mortality with Medical Care
• Huge Risk of Spreading Infection to Others
• Very Sick Patients - Lots of Resources
• Cannot Treat Mass Casualties
• Vaccinia
• VIG - more will have to be made
• Less sick patients - longer time

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Complications Last time - 1947 New York Outbreak

• Case from Mexico
• 6,300,000 Vaccinated in a Month
• 3 Deaths from the Smallpox
• 6 Deaths from the Vaccine
• Would Have Been Much Higher Without Vaccination?

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What would happen now?

• Assume 1,000,000 Vaccinated in Mass Campaign with
  No Screening
• Assume 1.0 Immunosuppressed
• 10,000 Immunosuppressed Persons
• Probably Low, Could be 2
• Potentially 1-2,000 Deaths and More With Severe
  Illness