This method may fall under the category of "nothing new under the sun," but I have not been able to find that the simple principles followed have ever been put into practice before. The idea of perfecting a new method of preparing the skin for inoculation was brought to my mind because of my sympathy for little children who are frightened and even given pain by the old, scarification plan.
The protection from absorption possessed by the skin is due to the epidermis and chiefly to the horny layer. This being removed, or even scarified, permits absorption. An excoriation or denudation is necessary to local infection in most cases, though follicular inoculation has been credited. Given, then, an impermeable covering, it was but necessary to find an agent which would dissolve or disintegrate the upper layers of the epidermis without pain or fright to the patient. Salicylic acid in glycerin
HUTCHINS MB. A SIMPLE, PAINLESS AND PERHAPS NEW METHOD OF VACCINATION; DENUDATION VERSUS SCARIFICATION.. JAMA. 1898;XXX(17):971-972. doi:10.1001/jama.1898.72440690031002i