The Balmis vaccine expedition

Smallpox had repeatedly struck Spain's royal family. After it disfigured his daughter María Luisa Carlota, Carlos IV had the other royal children inoculated, and a decree of 30 November 1798 extended inoculation to his subjects. Jenner's cowpox vaccine followed quickly: Francisco Piguillem vaccinated in Puigcerdà on 3 December 1800. Francisco Xavier de Balmis (1753 to 1819), chamber surgeon to the king, persuaded Carlos IV to send the vaccine to the colonies in a human chain.

The corvette María Pita left La Coruña on 30 November 1803 with 22 orphan boys aged three to nine. Fluid from the cowpox sores of vaccinated boys was used to vaccinate the next ones, so the vaccine stayed alive at sea. Isabel Zendal, director of the Charity Orphanage in La Coruña, cared for them. After a month in Tenerife the ship reached San Juan, Puerto Rico, on 9 February 1804.

The expedition was not always first. In Puerto Rico the military surgeon Francisco Oller had already vaccinated more than 1,500 people with vaccine sent through the Danish island of St. Thomas, and vaccine had also reached Cuba, Yucatán, Guatemala and Mexico City before Balmis. In Venezuela he divided his team on 9 April 1804, sending his deputy José Salvany to South America, and on 23 April the Central Vaccination Board of Caracas was founded, the model for boards set up wherever the expedition went.

Salvany's party vaccinated more than 2,000 people in Cartagena de Indias and recorded 56,324 vaccinations by the time it left Bogotá in March 1805. Salvany lost his left eye on the way and died in Cochabamba in 1810. Balmis went on through Cuba and Mexico, left for Acapulco at the end of 1804 with two dozen Mexican children to carry the vaccine across the Pacific, and reached Manila on 16 April 1805. He took the vaccine on to Macao and Canton and to the island of St. Helena, landed at Lisbon on 14 August 1806, and was received by Carlos IV in Madrid on 7 September. The History of Vaccines project puts the number vaccinated by the expedition at about 500,000.