The Balmis Expedition, directed by Dr. Francisco Javier Balmis, was a pivotal public health mission launched from Spain with the intent of eradicating smallpox in Spanish America and the Philippines. Smallpox had a devastating impact on populations worldwide, and the introduction of vaccination provided a hopeful solution. Balmis, accompanied by a team of medical personnel, sought to distribute the smallpox vaccine using an innovative method—transporting live vaccine lymph in arms of orphan boys. This challenging undertaking stemmed from intercontinental barriers, but reflected Enlightenment ideals of science and philanthropy aimed at improving the health of colonial subjects.

The Expedition embarked in 1803 from La Coruña, Spain, and involved a lengthy voyage across the Atlantic to various locations including modern-day Mexico, Cuba, Venezuela, and eventually the Philippines. The dedication of Balmis and his team was evident as they faced numerous challenges, including harsh seas, varied climates, and the logistical difficulties of vaccinating populations in remote areas. The mission not only aimed to vaccinate the population but also to train local medical personnel in vaccination techniques, ensuring sustainability.

The impact of the Balmis Expedition was far-reaching; it established the groundwork for future vaccination campaigns in Latin America and reinforced the importance of vaccination in public health. The expedition is often regarded as one of the first instances of a large-scale public health intervention across multiple territories, showcasing the possibilities of collective health responsibility and international cooperation.