A doctor vaccinates a child in the usual manner. At the end of four or five days, the dressing is taken from the arm, and the only thing to be seen is a little black scab. The child scratches this off. In a few days the spot becomes red and a small abscess forms, resembling a smallpox sore. Naturally, this is taken for a completely successful vaccination, but it is not really so. When the child scratched off the scab, the vaccination wound was nearly healed, and the little abscess was caused by some very mild pus germs, which were under the finger nails with which he scratched the wound. The abscess was in no wise connected with the vaccination, but was simply such an infection as a child might get at any time that he scratched his arm. No one has ever claimed that such an abscess will prevent smallpox any more than that a boil will prevent it. _A successful vaccination will prevent smallpox._ The length of time for which it will prevent the disease varies in different individuals. Some it will protect only for a year or two, while in others it will last through life. Dr. H. W. Bond, Health Commissioner of St. Louis, Missouri, states: "The experience of this department, based on the observation of thousands of cases, is that a well-pitted mark gives at least ten years' immunity. We have never seen a case of smallpox in a person with a well-pitted scar less than ten years old--that is, the scar less than ten years old." [Sidenote: A sore arm not always due to successful vaccination] One of the strongest objections made against vaccination is that the arm sometimes becomes very sore from it. This is true, but the sore arm is not a common occurrence and is never caused by vaccination properly performed. There is always some cause for the bad arm besides the vaccination. [Sidenote: Cause of sore arms] The usual cause of a bad arm is improper vaccination; this means the lack of proper precautions on the part of the person who does the vaccinating. Years ago, before vaccination was performed with the great care which is given it to-day, bad arms could not be prevented; but to-day the cause of the trouble is not the vaccine, but the vaccinator. Sometimes a father thinks he will save a dollar by vaccinating his child himself, and he is likely to injure the child by attempting to vaccinate him without taking antiseptic precautions. The same surgical preparations must be made for a vaccination as for an operation. If this is not done, a bad arm will result, not because of the vaccination, but because of the negligence of the vaccinator.