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Scientific and Policy Considerations in Developing Smallpox Vaccination Options: A Workshop Report
ing the multiple-puncture technique with a bifurcated needle. A reformulated vaccine, produced by using cell-culture techniques, is now being developed.
In fall 2001, there were 150,000 ampules of Dryvax, available at 100 doses per ampule, which would vaccinate 15 million people. However, because Dryvax is a dried product, once reconstituted it begins to deteriorate at a rapid rate, so there is a finite period of time in which it can be used, which can create substantial wastage. In September 2001, DHHS placed an order for 40 million doses of vaccine with Acambis, Inc. The 20-year contract would purchase a new vaccine produced in tissue cell culture, to be available in 2004. However, the September 11, 2001, attacks and the release of the anthrax organisms through the mail spurred the government to acquire more vaccine more quickly. Acambis and Baxter are currently producing 200 million doses of a stable tissue cell culture vaccine to be available by the end of 2002. Also in 2002, Aventis Pasteur located in a storage facility 85 million doses of vaccine prepared from calf lymph, produced in 1958. This vaccine has been tested and is available if needed; however, the newer vaccine produced in tissue cell culture is preferable.
Now that sufficient vaccine will be available for the entire U.S. population should it be needed, a responsible immunization strategy must be developed. Previous experience with immunization has shown that serious complications can arise in as much as 20 percent of those who come in contact with vaccinees but are not yet vaccinated and are susceptible to complications for a variety of reasons.
SCIENTIFIC BACKGROUND ON SMALLPOX AND SMALLPOX VACCINATION
The last case of naturally occurring smallpox occurred almost 25 years ago, and 24 years ago the last episode occurred in Birmingham, England, with the laboratory escape of variola virus. As a result of its eradication, virtually all clinicians, particularly in northern countries, are unfamiliar with this disease and research on human smallpox has practically stopped. Eradication was relatively easy to achieve because humans are the only reservoirs and vectors, the disease is clinically manifest, and there is no carrier or latent state. Moreover, one episode gives lifelong protection, transmission occurs when the disease is manifest, there is a stable vaccine, and it is relatively straightforward to trace chains of transmission.
This section summarizes the presentation by Joel Breman, Fogarty International Center, National Institutes of Health.