The military was giving smallpox vaccines to people deploying to the Mideast around 10-15 years ago. They would stick a little needle thing that was coated with cowpox to infect the patients arm. If the patient never had this vaccine they would be stuck with the sticker 25 times (iirc). The people that had had the vaccine as a kid would have to be stuck 50 or 75 times. The wound would begin to ooze puss and you were not supposed to bandage it.