ABSTRACT
During the 19th century, smallpox vaccination became increasingly popular and accepted in other areas, including Europe and North America (4). A remarkable and often forgotten global public health campaign was the Royal Philanthropic Expedition of the Vaccine commissioned by King Charles IV of Spain and directed by the physicians Francisco Xavier de Balmis and Jose´ Salvany, that between 1802 and 1806 took the smallpox vaccine to Spain’s territories in the Americas and the Philippines (12,13). It is fitting that smallpox became the first (and so far the only) communicable disease to be actively eradicated, an accomplishment achieved in the decade 1967 to 1977. An enigma that remains unresolved after the eradication of smallpox concerns the origin of vaccinia, the smallpox vaccine virus. Whatever its origin, vaccinia is a separate species within Orthopoxvirus genetically distinct from both cowpox and variola viruses. Cowpox is in fact a rodent virus that occasionally infects other mammalian hosts (14). Hypotheses that have been promulgated include that it represents a hybrid between cowpox and variola virus, that it derives from cowpox virus, or that it is a descendant of a virus (perhaps of equine hosts) that
Figure 1 Edward Jenner (1749-1823), the father of vaccinology. An 1800 pastel portrait of Edward Jenner by J. R. Smith. Source: Photo courtesy of The Wellcome Institute Library, London, U.K.
