In connection with the psora theory is the following opinion expressed by Hahnemann regarding vaccination.

In writing to Dr Schreeter, of Lemberg, on December 19, 1831, he says, “In order to provide the dear little Patty with the protective cow pox, the safest plan would certainly be to obtain the lymph direct from the cow; but if this cannot be done (children are also made more ill from it than from the matter obtained from human beings), I would advise you to inoculate another child with the protective pox, and as soon as slight redness of the punctures shows it has taken, I would immediately for two successive days give Sulphur 30, and inoculate your child from the pock that it produced. As far as I have been able to ascertain, a child cannot communicate psora whilst under the action of Sulphur.”

Dr Schreeter in a note to this letter says that he has found this advice to be true and has acted upon it in vaccination with good results.