Chapter 3 focuses on Jenner and the discovery of vaccination, specifically his translation of the vague notion that cowpox prevented smallpox into a more precise body of knowledge which could distinguish between varieties of cowpox and be the basis for the development of protocols for its effective use. Given the rarity of cowpox, his use of humanised cowpox (vaccine), propagated on children, was to prove critical to the success and viability of the practice. Publishing his findings in 1798, Jenner had to wait a year for his new mode of prophylaxis to gain acceptance. Initially, London-based physicians – Woodville conducting clinical trials and Pearson distributing vaccine – made much of the running. Jenner, however, reasserted his leadership in the field and made championship of vaccination his principal occupation. After considering reports on Jenner’s discovering of cowpox inoculation and making it available to the world, the British parliament granted him a premium in 1802. The Royal Jennerian Society was established in 1803 to promote and support the practice.

Chapter 4 discusses the expansion of vaccination in the British Isles during the Napoleonic Wars. The rapid extension of the practice from 1800, involving hundreds of thousands of people, represented a mobilisation of opinion and action that paralleled the mobilisation of the nation for war. Medical men took up vaccination with alacrity, seeking to make their name and serve their communities. Members of the aristocracy and gentry, with women often in the lead, accepted it in their families and supported it in their spheres of influence. Clergymen promoted it from the pulpit. Reckless practice led to adverse outcomes that encouraged anxieties about inoculating cowpox and provided ammunition for an anti-vaccination movement in London in 1805–7. Instructed to conduct an enquiry, the College of Physicians fully endorsed vaccination in 1807. After receiving the report, Parliament broke new ground in health provision by funding a National Vaccine Establishment to distribute vaccine and have oversight of the practice.

Chapter 14 returns to Britain in 1814–15, with Jenner hoping that peace would bring new opportunities to advance the vaccination cause. The end of the Napoleonic Wars and the reopening of lines of communication, bringing further reports of vaccination around the world, provides a useful vantage-point to identify key developments in the global story. Although the early history of vaccination is one of the diffusion of know-how and biomatter along the lines of Europe trade and empire, the networks rapidly become more complex and multilateral, with the new prophylaxis constructed on a global stage, not least the management of the practice, its integration in systems of public health and in legislative and other forms of coercion. Above all, it is possible to see vaccination as a quiet revolution, an emancipatory force, the pointy end of increasing state power and a foundation for further breakthroughs in the struggle against disease.

Chapter 1 introduces smallpox and, its ultimate nemesis, cowpox. At the beginning of the modern age, a more virulent strain of smallpox spread around the world. Observing that survivors did not take smallpox a second time, many cultures recognised that exposure to a mild case might prove advantageous. The practice of smallpox inoculation, first observed in Istanbul, was the focus of interest in western Europe and was introduced experimentally in the English-speaking world in the 1720s. Though not without risks, inoculation led to advances in understanding contagion and improvements in therapy. It also helped clarify the relationship between similar human and animal diseases. The expansion of inoculation in the eighteenth century revealed individuals whose resistance to smallpox infection was associated with prior cowpox infection. Jenner used inoculation to put the notion that cowpox prevented smallpox to the test. Familiarity with the old practice set the scene for the rapid introduction of cowpox inoculation, a milder intervention.