The introduction recounts the experiences of French physician Esteban Morel, who arrived in Mexico City in 1778 and immediately set about introducing inoculation among the upper classes during an epidemic of smallpox. Reluctant parents and rampant rumors of deformity and death stymied the inoculation campaign that year and suggest the critical role of nonprofessionals in colonial Mexico in healthcare reform. In an age when European monarchs looked to govern from above the health of populations, the perspectives and sensibilities of laypeople in the socially heterogeneous barrios, subdistricts, and rural regions of New Spain remained pivotal. Experiments with disease and its control were critical moments in which amateur scientists, physicians, corporate sponsors, and lay communities came together to assess the merits of reform and the relevance of Atlantic practices and projects for their own lives.

From 1736 to 1739 an outbreak of matlazahuatl, likely typhus, ravaged the Valley of Mexico. In Mexico City, public responses in the form of hospital care, processions, and numerous devotional acts were documented by Cayetano Cabrera y Quintero, an eyewitness and promoter of the cult of the Virgin of Guadalupe. His plague chronicle provides a point of departure for a deeper history of the dramaturgy of epidemic outbreaks, in which public pageantry and appeals to beloved saints transformed cities and towns into thoroughfares of saints and devotees. This chapter examines how these performances were both sponsored by corporate bodies and solicited by laypeople well into the eighteenth century, when administrators aggressively pursued sanitation and hygiene campaigns alongside divine succor.

Practices of publication and experimentation in the Atlantic world inspired physicians, natural philosophers, clerics, and others conversant in learning about climatic conditions, sanitation, and the sciences of anatomy, botany, chemistry, and statistics to forge connections with one another and with lay communities to improve medical care in New Spain. Beginning in 1768, the rise of a scientific periodical press in New Spain provided a novel means to collect and disseminate learning about health care, natural remedies, and scientific developments. In effect reproducing a conceit of colonial healing manuals, the print culture of the Enlightenment went further to shape a repository of vernacular knowledge from correspondents in cities, towns, and villages. Ultimately this venue failed to incorporate, as some hoped, a broader sector of the lower classes into scientific and medical practice.

At the end of the century the viceregal government mandated anticontagion measures for communities and households affected by infectious disease. Finally implemented in 1796 and 1797 with the arrival of another epidemic of smallpox, the regime occasioned radical experiments in disease management and a turn to new medical paradigms of prevention. Judicial inquiries, administrative correspondence, and legal briefs and petitions filed by guilds, village leaders, religious orders, and administrators conveyed the complaints and perspectives of peasants, artisans, merchants, priests, and district governors as they struggled over disease management in the intendancy of Oaxaca. Following months of social unrest, the viceregal government confirmed the technological shift already under way in rural villages by endorsing inoculation's widespread use.

Historians of science observe that new technologies must be "domesticated" before they work. Drawing on these insights, this chapter shows how immunization was first introduced in medical treatises, sermons, pastoral letters, legal briefs, and public ceremonies, as physicians, bishops, governors, and ministers aimed to convince parents and other caretakers of its value. These colonial genres and rituals, and eventually gifts of coins and cookies to entice parents and children, rendered preventive medicine safe, efficacious, and sacred for diverse publics and paved the way for the Royal Philanthropic Vaccination Expedition's introduction of Edward Jenner's cowpox vaccine.

Ceremonies to welcome vaccination teams and coax parents to submit their children were short lived, and in the chaotic decade of insurgency (1810–1820)—a time of acute warfare, infection, and famine—the ability of a shattered colonial government to sustain programs of disease prevention was overwhelmed by a perennial shortage of funds. This chapter draws on newly available records of vaccination campaigns in Mexico during the insurgency to consider the kinds of healing skill and expertise involved in the propagation of vaccine in these years. Priests, female healers, Spanish administrators, and Indian governors, as well as barbers and surgeons, helped coordinated vaccinations in campaigns that adhered to the dictates of disease outbreaks and warfare as often as those of medical professionals.

The final chapter returns to the experience of medical reform in pueblos de indios, where rumors and political rituals mediated enlightened techniques, personnel, and reform programs. Political rituals allowed parents and Indian officials to assess and judge these medical interventions, discern efficacy, and occasionally shape more acceptable campaigns. Rumors of enslavement, forced enlistment, witchcraft, and kidnapping had the effect of threatening flight from villages by parents and others into "regions of refuge," which compelled negotiation by administrators to avoid aborted campaigns and lost revenue. In these ways laypeople were integral to the domestication and interpretation of Enlightenment treatments.

At the end of the nineteenth century, doctors and scientists in Mexico helped the authoritarian government of Porfirio Díaz project an image of a modern nation to the world. Despite medicine's professionalization, a dispute in downtown Mexico City in these years over whether the sacred spaces of a parish church might be used for vaccinations opens a window onto continued confusion over preventive medicine's proper place and identity. In part, confusion was a result of the role of rural priests in disease management and medical practice; early vaccination campaigns only reinforced the overlapping of authority in the early Republic. Continued struggles to immunize the population against disease in the nineteenth century warn against the tendency to see medical empiricism as neatly opposed to religious agents, rituals, or administration in the modern period.