Infectious Disease · 1796
Jenner's smallpox vaccination (cowpox inoculation)
Before 1796, the only available protection against smallpox was variolation: deliberate inoculation with material taken directly from a smallpox pustule. The procedure conferred immunity in most cases but carried a real risk of causing fatal disease, and vaccinated individuals could transmit smallpox to contacts during the incubation period. Edward Jenner, a country physician in Berkeley, Gloucestershire, had spent years gathering anecdotal reports from local dairymaids who seemed resistant to smallpox after contracting the milder cowpox. The observation was not new among rural English farmers, but no one had tested it systematically.
On May 14, 1796, Jenner inoculated eight-year-old James Phipps with material taken from a cowpox pustule on the hand of milkmaid Sarah Nelmes. Six weeks later, he exposed the boy directly to smallpox material. Phipps remained well. Jenner repeated the test and then spent the next two years collecting similar cases before submitting his findings for publication. His 1798 monograph, "An Inquiry into the Causes and Effects of the Variolae Vaccinae," documented 23 cases in which cowpox exposure appeared to protect against subsequent smallpox challenge.
The Royal Society initially declined to publish Jenner's first paper, and early reception among London physicians was skeptical. The concern was reasonable: Jenner's sample was small, his mechanism was unknown, and some early replicators used contaminated or degraded material and got inconsistent results. Nevertheless, the practical advantages over variolation were obvious enough that uptake began quickly. By 1800, vaccination programs were underway in several European countries, and Napoleon ordered the French army vaccinated in 1805.
The principle Jenner described, using a related, attenuated pathogen to prime immunity against a lethal one, became the conceptual template for vaccine development. The term "vaccine" derives from vacca, the Latin word for cow, a direct acknowledgment of Jenner's original material. Mass campaigns using successive generations of the method continued across two centuries. In 1967, the World Health Organization launched its intensified smallpox eradication program; in 1980, it declared smallpox eradicated, the only human infectious disease to have been eliminated entirely from nature.
Key People
- Edward Jenner — Country physician who designed and documented the cowpox inoculation experiment
- James Phipps — Eight-year-old subject of Jenner's first inoculation, 1796
- Sarah Nelmes — Milkmaid whose cowpox pustule provided the inoculation material
- Napoleon Bonaparte — Ordered French army vaccination in 1805, accelerating European adoption
Jenner E. An Inquiry into the Causes and Effects of the Variolae Vaccinae. London, 1798.
Related landmarks
- 1882 · Koch's Discovery of the Tubercle Bacillus (Infectious Disease)
- 1928 · Fleming's discovery of penicillin (Infectious Disease)
- 1955 · Salk Inactivated Polio Vaccine Field Trial (Francis Report) (Infectious Disease)
- 1960 · Sabin Oral Live-Attenuated Polio Vaccine (Infectious Disease)