Most historians document the first recorded vaccination to be around 1796 when Edward Jenner vaccinated a small boy against smallpox virus. He got the idea for vaccination when he saw that milkmaids working in close proximity with cows were completely immune to the smallpox virus. He thought that this could mean if someone's body was exposed to the cowpox virus their body was immune to the smallpox virus because it had already encountered a similar disease. Edward Jenner tested his vaccine on a small boy by injecting a trace of cowpox virus into him. After a few days of mild sickness he became immune to the smallpox virus. Jenner then vaccinated several more people against smallpox and did regular tests on their immunity to the disease which
