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After eradication, there is a small but finite risk that smallpox and/or poliomyelitis viruses could accidentally escape from a laboratory or be released intentionally. The reintroduction of either virus into a highly susceptible population could develop into a serious catastrophe. To counter such an occurrence will require the use of vaccine, perhaps in substantial quantities. In the United States, new stocks of smallpox vaccine are being procured and arrangements are being made for a standby production facility. Similar provisions need to be considered for polio. To counter an epidemic of polio will require the use of the oral vaccine, which is presently the World Health Organization-recommended vaccine of choice for countries throughout the developing world. In these countries, its continued use is advised because of its ability to induce intestinal immunity, its ability to spread to other susceptible household members and to protect them, its ease of administration, and its low cost.