Why Smallpox Bioterrorism n n n Stable aerosol

Why Smallpox Bioterrorism? n n n Stable aerosol Virus Easy to Produce Infectious at low doses Human to human transmission 10 to 12 day incubation period High mortality rate (30%) n CDC Materials

• Small Pox Vaccine History n n n 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 1940’s - Development of commercial process for freeze-dried vaccine production (Collier)

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

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

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

Historic Probability of Injury n n n Small Risk from Bacterial and Viral Contaminants Small Risk of Allergic Reaction 35 Years Ago n n n 5. 6 M New and 8. 6 M Revaccinations a Year 9 deaths, 12 encephalitis/30 -40% permanent Death or Severe Permanent Injury 1/1, 000 n Mostly among immunsupressed persons

Global Eradication Program n n 1950 - Pan American Sanitary Organization initiated hemisphere-wide eradication program 1967 - Following USSR proposal (1958) WHO initiated Global Eradication Program n n n 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

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

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

How Have Risks Changed? n n n Immunosuppressed Persons Cannot Fight the Virus and Develop Progressive Vaccinia Immunosuppression Was Rare in 1970 Immunosuppression is More Common n HIV, Cancer Chemotherapy, Arthritis Drugs, Organ Transplants

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

Complications Last time - 1947 New York Outbreak n n n 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?

What would happen now? n n Assume 1, 000 Vaccinated in Mass Campaign with No Screening Assume 1. 0% Immunosuppressed n n n 10, 000 Immunosuppressed Persons Probably Low, Could be 2%+ Potentially 1 -2, 000+ Deaths and More With Severe Illness