After this time, it became known to him that dairymaids did not have smallpox. He was impressed to find out that a person who had cowpox did not get infected with smallpox. Jenner spent some thought on this and concluded that cowpox could not only prevent people from contracting smallpox, but could also be transmitted to other people as a source of protection from the deadly disease. After discovering this, Jenner decided to test his theory. On May 1796, he took a fresh cowpox pustulate from Sarah Nelmes, a young dairymaid, and inoculated James Phipps, an eight-year-old boy who was free from smallpox. Phipps became slightly I'll for a few weeks, but he eventually got better. Jenner then inoculated Phipps again, this time with the smallpox pustulate. After some time, no smallpox disease developed in James