Organon §33

Experience shows that medicinal energies affect health unconditionally while natural disease energies only affect health under certain conditions.

It proceeds undeniably from all experience 74 that the living human organism is far more disposed and inclined to allow itself to be aroused and have its condition differently tuned by medicinal powers than by ordinary disease malignities and infectious miasms. In other words, disease malignities possess a power to differently tune the human condition which is subordinate and conditional, often very conditional, while medicinal energies possess an absolute unconditional power far outweighing the power possessed by disease malignities.  

Comment
74 The following is a striking example of this: Until 1801, epidemics of scarlet fever (i.e. , Sydenham’s smooth scarlatina) still reigned. They broke out from time to time and befell, without exception, all children who had not weathered it in a previous epidemic. However, in the Kцnigslutter epidemic which I experienced, all the children who took a very small dose of Belladonna early enough remained free of this highly contagious childhood disease. If medicines can protect us from the contagion of a raging disease, so must they possess a preponderant power to differently tune our life force.