Advances in the Immunoprophylaxis of Smallpox1
PAUL FENJE2
IT is a unique case in the history of medicine when a method and its means for application survive for 160 years almost unchanged, particularly when these 160 years represent a complete revolution in thought and approach to most medical problems. However, this is the case with smallpox vaccination and with the smallpox vaccine, which is even today basically prepared in a very similar way to that devised by Dr. Duquemelle in Rheims, France, in the first decade of the last century (1, 2, 3).
However, this does not mean either that the vaccine is so satisfactory that it needs no improvement or that the tremendous amount of research concentrated on smallpox vaccine was without results. Although in the last twenty years progress in this field has been less dramatic than in other fields of immunoprophylaxis of virus diseases, such as poliomyelitis or measles, laboratory research and field investigations have cleared up many points which were passed from generation to generation of medical people in some kind of mythical form, or at least in dogmatic terms (4).
One of the very much discussed and extremely controversial subjects in this field was the nature and origin of the vaccinia virus itself. At the present time, the generally accepted view is that vaccinia virus represents a separate entity in the group of the animal pox viruses, which includes both mammalian and fowl pox viruses. The interrelationship among the various members of the mammalian pox viruses is a very close one (5). Morphological differences are almost non- existent; they share several common antigens, although they appear to be serologically distinct. Nevertheless, at one point they can be differentiated: in their host range, in their ability or inability to infect and multiply in various laboratory and non-laboratory animals. Taking all this into account, it appears that vaccinia virus is most closely related to the cowpox virus from which it most probably originates. Phylogenetically the whole group derives probably from one common ancestor and its differentiation must be connected with the domestication of animals by the first agricultural settlers of the human race (6).
The difficulty of tracing the origin of vaccinia virus strains may be exemplified by the history of the Lister Institute's vaccine strain, which is currently used in Great Britain. Allegedly it came from France, where it had been isolated from a soldier who contracted smallpox during the Franco-German war in 1870 (1). Different vaccine-producing laboratories propagate their virus strains in various animals, mostly ruminants like calves, sheep or water buffaloes, or in rabbits.
1 Presented at the Seventh Annual Refresher Course, School of Hygiene, University of Toronto, February 10-14, 1964.
2 Research Associate, Connaught Medical Research Laboratories, University of Toronto, Toronto 4, Ont.
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