The concept of vaccination dates back hundreds of years, long before the discovery of germs or the modern immune system. In 1796, Edward Jenner, an English physician, observed that milkmaids who had contracted cowpox—a mild disease transferred from cattle—did not catch smallpox, a deadly viral infection that was ravaging Europe. Hypothesizing that the cowpox provided protection, Jenner extracted fluid from a cowpox blister on a milkmaid’s hand and inoculated an eight-year-old boy named James Phipps. Months later, Jenner exposed the boy to smallpox multiple times, but Phipps never developed the disease. Jenner coined the term 'vaccine' from the Latin word *vacca*, meaning cow. Although his methods would be considered unethical by today's standards, his work laid the foundation for immunology. It wasn’t until nearly a century later that Louis Pasteur expanded this principle. Working with cholera in chickens, Pasteur discovered that weakened (attenuated) bacteria could stimulate immunity without causing severe disease. This led to the development of vaccines for anthrax and rabies. Today, vaccines utilize various methods, including mRNA technology, but the core principle remains the same: training the immune system to recognize a pathogen so it can fight it off in the future.