In 1796, Edward Jenner famously took pus from a cowpox pustule of a milkmaid and injected it into his gardener’s 8-year-old son, James Phipps. Cowpox was a comparatively harmless condition that farmworkers would contract from their charges, but it was related to the far deadlier disease of smallpox, which killed thousands each year. After a few days, Jenner proceeded to deliberately infect James with the deadly smallpox. Luckily for the boy, Jenner’s hunch proved correct: People who had a case of cowpox gained immunity against smallpox. The brave subject doubtless got a pat on the head, while Jenner won fame and prizes.
Jenner himself suggested that “the annihilation of … the most dreadful scourge of the human species” would be the final result of his invention. But that would take the global spread of vaccination—including to the Americas. Smallpox arrived in the New World soon after Columbus, and was one of the Old World diseases responsible for wiping out the considerable majority of the population of North and South America in the century after his voyages. But efforts to send vaccine material across the Atlantic in sealed glass were largely unsuccessful—temperature and time killed the cowpox virus. In 1803, a scant seven years after Jenner’s experiment, King Charles IV of Spain sponsored the “Royal Philanthropic Expedition of the Vaccine” to ensure the treatment was delivered across his empire, and put the effort under the direction of one of his physicians, Francisco Javier de Balmis.
Balmis left Spain on the corvette Marίa Pita on Nov. 30, 1803, with assistants, nurses, and staff, as well as 20 unvaccinated children from La Coruña’s orphanage, who would be infected in turn by cowpox on the journey. Children ages 3 to 9 were used because they could be more easily guaranteed to have avoided previous exposure to smallpox—that would make them ineffective vaccine carriers. They were carefully isolated until their turn to be injected with pus, two at a time, all across the Atlantic. Vicente Ferrer (7) and Pascual Aniceto (3) were the first two children vaccinated. Along with the orphans, Balmis brought 2,000 copies of a treatise on vaccination. They would provide guidance to the vaccination boards that the expedition would create to ensure a continuing reservoir of vaccines and local distributors.