Edward Jenner Case Study

The smallpox virus plagued humans for thousands of years, resulting in millions of deaths worldwide, before Edward Jenner stumbled upon a way to eventually eradicate the disease. The disease devastated populations across Asia, Africa, Europe, and eventually the Americas through the voyages of discovery. The number of Aztecs and Native Americans killed by the virus is far greater than the number killed in battles with white settlers. The virus had a fatality rate of approximately 30% while survivors were often left with permanent scarring, deformities, and blindness as a result of the disease. Before Jenner's vaccine, practitioners in Asia developed a method known as variolation that was eventually brought to England in 1721 by Lady Mary Wortley Montagu after spending time abroad in Turley. This became the

standard for preventing the spread of the virus, a process by which smallpox material was taken from an infected patient and given to an individual who would then develop a milder form of the disease. Variolation was done in the hopes that the individual would then be protected from the virus due to the fact that they had already been infected. However, identifying a suitable strain of the disease was extremely difficult and it was not uncommon for deaths to occur as a direct result of variolation. It would seem that the disease was simply too great to be defeated, until Jenner took note of an interesting phenomenon concerning milkmaids and cowpox.
Cowpox is a relatively mild viral infection in cows that was occasionally spread to milkmaids from sores on the udders of cows. Though the milkmaids would develop some pocks and feel unwell for a few days, the disease was relatively harmless. One such milkmaid came to Edward Jenner for treatment of a rash on her hand. During the appointment, he became privy to a bit of lore that had been widespread amongst dairy farmers for centuries; cowpox gave one immunity to smallpox. Pustules similar to those found on cows suffering from cowpox developed on milkmaids and cowherds upon being infected by the disease. When these milkmaids were inoculated with small pox, they developed virtually no symptoms of the disease. Jenner had unknowingly stumbled upon the secret to fighting smallpox, writing that “what renders the cow-pox virus so extremely singular is that the person who has been thus affected is forever after secure from the infection of the smallpox; neither exposure to the variolous effluvia, nor the insertion of the matter into the skin, producing [smallpox].” What came next was a series of empirical observations and experiments, allowing him to harness the immunity powers of cowpox to develop a vaccine to prevent the spread of the disease.
Jenner wrote of fourteen different cases explaining his observations and experimentations of the interactions of cowpox and smallpox.

Case I concerns Joseph Merret, a former servant that assisted with milking cows who contracted cowpox in 1770. Merret was inoculated with his family twenty-five years after suffering from the disease whilst several of his family members suffered from smallpox, but he himself did not develop any symptoms of the disease. Jenner takes the time to explain that due to the fact that the population was thin where Merret lived that he was able to ensure that no one whose case is recorded had previously suffered from smallpox. Case II speaks of Sarah Portlock, who’d been infected twenty-seven years prior to nursing her smallpox-infected child. Variolous matter was inserted both of her arms, but she remained uninfected. Case V is of Mrs. H—, who contracted cowpox from handling utensils also used by the servants of the family. She was later exposed to smallpox while caring for an ill relative who fell to the disease, yet she never developed symptoms of the disease. She was inoculated with active variolous matter and still remained

uninfected.
Case VI was of a reversed situation in which several were infected with cowpox, but they were unharmed due to the fact that they had survived smallpox years before. “The whole of the family…had gone through the small-pox…the consequence was that [they] escaped the infection of the cow-pox entirely…but the other dairymaid, Sarah Wynne, who had never had the small-pox, did not escape in so easy a manner.” She was later inoculated with the variolous smallpox matter and she did not contract smallpox. Case IX illustrates the susceptibility of humans developing cowpox, recounting how a man named William Smith became afflicted with cowpox on three separate occasions. He was twice inoculated, but never developed symptoms of smallpox despite associating with those suffering from smallpox “in its most contagious state.”
Case XII describes eight patients who’d previously had cowpox presenting themselves for inoculation. None of them received the variolous infection, which worked out since many of the poor women turned out to be pregnant at the time. Case XVII recollects Jenner experimenting on a healthy eight-year-old boy in order to accurately observe the progression of the infection. The boy was inoculated with cowpox, the matter taken from a sore on the hand of a dairymaid, and immediately fell ill. Nearly a month and a half later, the boy was inoculated with variolous matter of smallpox. No incident of smallpox occurred. He was then again inoculated with variolous matter several months later, but once again no effect was produced.
Case XVIII tells of a five-year-old boy inoculated with matter taken from a pustule infected from a mare’s heels—believed to be the source where the cowpox virus originates but not from where cowpox is predominantly caught. Jenner explains that the experiment was done to “ascertain the progress and subsequent effects of the disease when thus propagated.” He also discusses how the virus from the horse is not to be relied upon to “render the system secure from variolous infection,” but reiterates that thus far the matter produced upon the nipple of the cow still provided some level of protection against smallpox. The boy was never inoculated with smallpox, as shortly after he came down with a contagious fever soon after the experiment was conducted. In the several other cases following, Jenner continued to see that those previously afflicted with cowpox never developed symptoms of smallpox. Jenner’s theory had been tested several times over and thus it still stood to reason that cowpox could prevent the development of smallpox.
Upon completion of his empirical observations and experimentations concerning the link between smallpox and cowpox, Jenner intended to spread the word on his discovery to “lend scientific validity to humble folklore.” In 1798 he published An Inquiry Into the Causes and Effects of the Variolae Vaccinae, or Cow-Pox to chronicle his experiences leading up to the formation of his theory, as well as his observations and experimentations to test his theory. Though his results and the book were received with much ridicule, his method of vaccination grew in popularity and ultimately replaced variolation as the new standard practice to decrease the spread of smallpox.
Edward Jenner’s development of the smallpox vaccine paved the way for many scientists to later develop several other vaccinations against various diseases. The nineteenth and twentieth centuries saw scientists following Jenner's model to develop new vaccines to fight various deadly diseases including polio, whooping cough, the measles, and many others. Smallpox vaccines became more sophisticated throughout the years and by 1970 smallpox had been eradicated worldwide by several international vaccination programs.