The Smallpox Vaccination Program Public Health in an Age of Terrorism (2005) / Chapter Skim
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1 Smallpox and Smallpox Control in the Historical Context
1 Smallpox and Smallpox Control in the Historical Context
Pages 9-21
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From page 9... ...
. Smallpox is a highly infectious disease caused by the large and complex variola virus (one of the largest viral genomes known)
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A BRIEF HISTORY OF SMALLPOX The modern history of smallpox disease begins in the seventeenth century, with detailed records of cases and epidemics, as well as the earliest accounts of variolation, a precursor to contemporary immunization which involved inserting particles obtained from smallpox lesions under the skin or into the nostrils of a person who had never had smallpox. In the late eighteenth century, Edward Jenner discovered that dairy maids who had suffered and recovered from the less serious cowpox were not susceptible to smallpox infection, and he subsequently developed and refined the technique of removing material from a human cowpox lesion and transferring it to another person.
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Since that time, the virus has ceased to exist in the wild, with official repositories for live variola virus remaining only at two secure locations in Atlanta, Georgia, in the United States, and in Novosibirsk, Russia. Subsequently, the WHO Committee on Orthopoxvirus Infections planned a coordinated destruction of all existing stocks of smallpox virus, all stored clinical material containing virus, and all intact virus DNA in June 1999.
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. Before the eradication of the variola virus, ordinary type smallpox accounted for approximately 90 percent of cases in unvaccinated individuals and 70 percent in previously vaccinated individuals whose immunity had weakened over time (CDC, 2002b)
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. Vaccine Efficacy Experience documented during the global smallpox eradication campaign has shown that smallpox vaccine is highly effective, but its efficacy has not been measured with precision in controlled studies (CDC, 2003a)
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. Current research is still in its early stages and takes place in the absence of actual smallpox disease, relying instead on three surrogate measures of immunity: neutralizing antibody, cellular immunity, and skin reactions.
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From page 15... ...
The Vaccine Supplies Available in the United States At the time the military and civilian smallpox vaccination programs began in late 2002 and early 2003, respectively, the federal government had access to two stores of smallpox vaccine: 15 million doses of Dryvax in government storage since 1982, and 70-90 million doses of Aventis Pasteur vaccine available from the company (Lueck, 2002; Roos, 2002; CDC, 2003b)
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From page 16... ...
The case-fatality rate for smallpox vaccines in 1968 was one per one million primary vaccinations, and children had higher rates (number of events per million primary vaccinees) of severe vaccine-related complications when compared with primary vaccinees age 20 and older (Breman and Henderson, 2002)
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From page 17... ...
. Based on such historic data, 1,000 per million primary vaccinees would experience severe adverse events, and 14 to 52 individuals per million primary vaccinees would experience life-threatening reactions to the vaccine (i.e., eczema vaccinatum, progressive vaccinia, and postvaccinal encephalitis)
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Vaccination strategies that were successful in the past might be less successful in the contemporary context. Ring vaccination that was an effective means of controlling disease transmission among developing country populations that may have been significantly less mobile may not work for today's highly mobile populations.
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Although epidemiologic data about smallpox disease is substantial, one of the difficulties of relying on historic data to assess smallpox infectivity is the fact that these data were collected in a context of significant population immunity. As smallpox vaccination was discontinued, successive generations of children were born and grew to adulthood without vaccination, gradually decreasing the immunity of the population.
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2001. News Release: HHS Awards $428 Million Contract to Produce Smallpox Vaccine.
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Press Release: NIAID Study Results Sup port Diluting Smallpox Vaccine Stockpile to Stretch Supply. [Online]
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