Food for thought from the May 2005 Scientific American:
One novel solution to the lack of refrigeration for vaccines occurred 200 years ago, shortly after Edward Jenner discovered that cowpox infection acts as a vaccine against smallpox. In 1803 military doctor Francisco Xavier de Balmis embarked on an expedition ordered by King Charles IV of Spain. With a small team, he sailed from Spain to bring Jenner’s smallpox vaccine to the New World, where Spanish colonies were being devastated by the disease.
To preserve the vaccine, de Balmis harvested it from the 22 orphan children he brought along. He infected one child and waited about 10 days as pustules formed. De Balmis then took the fluid from the lesions and inoculated it into another child, continuing the cycle with successive immunizations. In this way, the vaccine reached Puerto Rico, Mexico and Venezuela. He also taught local doctors how to apply and propagate the vaccine.
De Balmis continued on to Spain’s colonies in Asia — picking up new children along the way and finding homes for the others now vaccinated — before returning home in 1806, while an assistant, José Salvany, reached Columbia, Peru and Chile. “Four or five years after de Balmis, between 100,000 and half a million people could have been immunized,” calculates Guillermo Olague, a historian of science at the University of Granada in Spain. “That marked the beginning of the end of the epidemic.”