With this in mind, Jenner took samples from the open cowpox sores on the hands of a young dairymaid named Sarah Nelmes and inoculated eight-year-old James Phipps with pus he extracted from Nelmes ...

This similar virus is cowpox. The cow to the left has been intentionally infected with cowpox virus. The fluid that you collect from virus-caused pustules on the cow's udder contains many copies ...

He suspected that they were prevented from getting the disease because they had previously contracted cowpox (a disease similar to smallpox, but less virulent) from their cows. Jenner inoculated 8 ...