詹納和他的同時代人如何在疾病的細菌學說之前了解疫苗接種?


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愛德華·詹納(Edward Jenner)是18世紀的英國醫生,他於1798年開發了"疫苗",將人暴露於牛痘中以防止他們獲得小痘。疫苗很快被接受,詹納被視為英雄。預防接種可以代替接種疫苗(實際上是將人暴露於減毒的小痘痘中)作為預防小痘痘的一種方法。

然而,疾病的細菌學理論直到1800年代中期才開始在巴斯德和科赫身上得到應用。在此之前,關於傳染性的疾病理論之間的爭論還是關於疾病是否僅僅是由人的環境引起的(疾病的氣喘病理論)之間的爭論。

因此,我不了解人們如何概念化/解釋暴露於小痘或牛痘所帶來的免疫力這一事實。人們在Pastuer和Koch之前就知道,暴露於天花意味著以後不會染上天花。他們當時如何通過對疾病的理解來解釋這一事實?除了觀察和發現接種和疫苗接種迅速普及的描述外,我沒有找到關於此事的任何評論,但當時我無法找到有關為什麼它們起作用的解釋的任何討論。

例如,愛德華·詹納(Edward Jenner)向皇家學會提交的有關疫苗接種的論文可以在這裡找到:https://biotech.law.lsu.edu/cphl/history/articles/jenner.htm

但是它們完全是經驗性的,很少解釋其疫苗為何起作用。

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The germ theory dates to late middle ages, and was favored by Avicenna among others, although it did not gain much currency in Europe until the mid 19th century. But it was not needed to discover the success of inoculations, which long predate Jenner, and which were later developed into more elaborate vaccinations. That much was established empirically, see Edward Jenner and the history of smallpox and vaccination by Riedel.

"It was common knowledge that survivors of smallpox became immune to the disease. As early as 430 BC, survivors of smallpox were called upon to nurse the afflicted (9)... However, the most successful way of combating smallpox before the discovery of vaccination was inoculation. The word is derived from the Latin inoculare, meaning “to graft.” Inoculation referred to the subcutaneous instillation of smallpox virus into nonimmune individuals... Inoculation, hereafter referred to as variolation, was likely practiced in Africa, India, and China long before the 18th century, when it was introduced to Europe".

Jenner himself was inoculated with smallpox in 1757, at 8 years old, developed a mild form of the disease, and recovered, so he needed no theory to be convinced. He became a learned man, but those were Newtonian times, when experimental evidence was valued over theoretical speculations in the spirit of hypotheses non fingo. Old school "explanations" were mocked, as in Moliere's "opium puts you to sleep because it has sleep-inducing virtue", and as Jenner's teacher John Hunter wrote in a letter to him:“I think your solution is just. But why think? Why not try the experiment?

So Jenner collected sixteen case histories since the 1770s, and staged twelve inoculation experiments of his own in 1796-97 instead. Even his idea of replacing infected tissue from human hosts by that from infected animals (which weakens the virus) came from empirical observations, and not theory, see The History Of Vaccines And Immunization by Stern and Markel.

This said, pre-Pasteur theories of inoculation's effectiveness did exist, even as Jenner had no interest in them, see A History of Theories of Acquired Immunity by Silverstein and Bialasiewicz. An early one, based on the humoral theory of disease is due to Rhazes (c. 900), and in Drake's 1707 theory smallpox can recur, but the symptoms do not manifest because the "morbid matter" would escape through the now extended pores and glands as fast as it forms.

In the 18th century, the age of inoculations in Europe, depletion theories came to be popular, which envisioned instead of imbalance of humors some external agent entering the body as the cause, and some depletable substrate in the body as enabling it. Fracastro offered an early such theory back in 1546, which relied on an early form of germ theory inspired by Avicenna:

"It was Fracastoro who first gave formal currency to the idea that not only was disease caused by small seeds (seminaria), but that the contagion might spread directly from person to person, indirectly by means of infected clothing, etc., or even at a distance... The seminaria of smallpox, he felt, not only had an affinity for blood as Rhazes had suggested, but more specifically they had an affinity for that trace of menstrual blood with which each of us was supposed to be tainted in utero, and which thenceforth contaminates our own blood. In this, Fracastoro picked up and expanded upon an idea advanced early in the 11th century by Avicenna... As with Rhazes’ theory, that of Fracastoro appeared to explain all of the known phenomena associated with smallpox, with acquired immunity in this case resulting from the expulsion during the first illness of the menstrual blood contaminant without which clinical disease could not recur."

Mather, best known for his role in the Salem witch trials, offered another such theory in 1724, but without identifying the external agent as some kind of germ. Kirkpatrick postulated a depletable “pabulum” in the blood, with which contagious “primordia” united (1754), and Gatti (1764) compared the body to dry wood that a single spark can set afire, but which becomes “incombustible” thereafter.