[The institutionalization of vaccination in Spain: from smallpox to the National Vaccination Schedule (1803-1975)].

Vaccination has played a central role in the historical development of public health in Spain and in the progressive institutionalization of state health intervention. From the late eighteenth century onwards, the fight against smallpox acted as a driving force for increasingly systematic preventive policies, evolving from variolation to jennerian vaccination and its administrative regulation. The Royal Philanthropic Vaccine Expedition (1803-1813) represented the first major milestone in this process, transforming vaccination into an organized, permanent practice under public authority. Throughout the nineteenth century, successive legal provisions consolidated this model, culminating in the creation of the National Vaccine Institute and in the establishment of compulsory vaccination and revaccination as structural public health policies. During the twentieth century, this framework was extended to other infectious diseases with major social impact. In the case of diphtheria, the introduction of antitoxin therapy and the subsequent development of active immunization led to the legal enforcement of compulsory vaccination in 1943. Later, the National Tuberculosis Eradication Plan (PNET), launched in the 1960s, represented the last major mass vaccination effort prior to the implementation of the National Vaccination Schedule, which integrated immunization into routine healthcare practice. This article examines the regulatory, institutional, and technical evolution of vaccination in Spain between 1803 and 1975, highlighting its key role in the consolidation of modern public health.