Under this Case Jenner observes, that “among our dairy farmers those who have had Smallpox either escape Cowpox, or are disposed to have it slightly; and as soon as the complaint shows itself among cattle, assistants are procured, if possible, who are thus rendered less susceptible of it, otherwise the business of the farm could scarcely go forward.” At the farm where Sarah Wynne was employed, all had had Smallpox except Sarah, and all save Sarah, escaped.
In 1796 had Cowpox. In 1797 was inoculated with Smallpox by Jenner without effect.
Under Rodway’s Case Jenner showed that the farmers were at fault in supposing that Smallpox kept off Cowpox. In the dairy where Rodway was employed, all the milkers had passed through Smallpox, except Rodway, and all contracted Cowpox; “but there was no comparison in the severity of the disease as it was felt by them and by Rodway. While he was confined to bed, they were able, without much inconvenience, to follow their ordinary business.” Thus Jenner argued that though Smallpox might not keep off Cowpox, it made Cowpox milder.
In 1759 had Cowpox slightly when 19 years of age. “As the malady had shown itself in so slight a manner,” observed Jenner, “and as it had taken place at so distant a period of her life, I was happy with the opportunity of trying the effects of variolous matter upon her constitution, and on the 28th of March, 1797, I inoculated her” without effect. Nevertheless in the following year, 1798, she again caught Cowpox, having a “large pustulous sore” accompanied with “general lassitude, shiverings, alternating with heat, coldness of extremities, and a quick and irregular pulse.”
Although [wrote Jenner as preface to this Case] the Cowpox shields the constitution from the Smallpox, and the Smallpox proves a protection against its own poison, yet it appears that the human body is again and again susceptible of the infectious matter of the Cowpox.
In 1780, when attending to Horses with sore heels, Smith conveyed the equine infection to Cows, “and from the Cows it was communicated to Smith. In 1791, the Cowpox broke out at another farm where he then lived as a servant, and he became affected with it a second time; and in 1794 he was so unfortunate as to catch it again. The disease was equally as severe the second and third time as it was on the first.” He was twice inoculated with Smallpox in 1795, and exposed to Smallpox without effect.