 Historians have found that the origin of vaccines goes back to ancient Asia and Africa. Early versions of what are now called vaccines are believed to have been discovered in response to a deadly disease known as smallpox, which was widespread across many cultures and countries and affected rich and poor people equally. Fortunately, vaccine-like treatments were developed to protect people against this sickness. In Asia, a technique known as variolation was used, involving a person being purposefully infected with smallpox by placing pus from a smallpox sore under their skin. This caused a milder disease than a full smallpox infection and resulted in the person gaining lifelong immunity. While widely practiced in Asia and Africa, this was viewed with skepticism by European physicians, and smallpox killed approximately 400,000 Europeans a year in the 18th century. In 1796, Edward Jenner, an English doctor, demonstrated that cowpox virus treatment could also prevent smallpox disease. This works because the two viruses look very similar to the human immune system, though Jenner did not know that at the time. Jenner injected an 8-year-old boy with pus he had taken from a cowpox sore on the hand of a milkmaid. The little boy had a mild illness, not at all dangerous like smallpox, and he recovered quickly. When Jenner later deliberately exposed the boy to smallpox, he didn't get sick. His immune system was trained to fight off smallpox infection because of his prior exposure to cowpox. A fun fact, Jenner created the word vaccine from the Latin word vacca, which means cow, and vaccinia, which is Latin for cowpox. Although injecting someone with pus caused by cowpox might sound gross, Jenner's discovery ultimately led to the development of modern smallpox vaccines and wiped out smallpox, an amazing public health achievement. It was also the beginning of more vaccination discoveries and development. Vaccine research continued to boom throughout the mid-20th century. Scientists began growing viruses in laboratories leading to new discoveries. One huge triumph of the time was the creation of the polio vaccine. Polio is a deadly virus that infects the central nervous system and can cause paralysis. It went from being a very common dangerous disease to one that is very rare because of the polio vaccine. The development of vaccinations have allowed researchers to combat other common and sometimes deadly childhood diseases such as measles, mumps and rubella. In fact, very few people in our day and age have heard of some of these diseases since vaccines have dramatically reduced the number of cases of these and many other childhood diseases. So at the end of the day, we owe a big thank you to the individuals who were injected with pus by doctors in Asia and Dr. Jenner. You helped to solidify the idea of training the immune system for future protection. And for that, we thank you. Due to the development of vaccines, diseases such as polio, measles and chickenpox are now preventable and parents no longer have to wash their children's suffer from these once common illnesses.