Vaccine is an immunomodulator that prevents microbial infection. The first vaccine was discovered by Edward Jenner.
The vaccine came to us through an excellent history. The concept of vaccine came from a milkmaid woman. She informed Edward Jenner that “she had suffered from cowpox and never get smallpox”. This information leads Jenner to an experiment for developing vaccine.
In 1796, he collected scrapings from cowpox blister and injected into a healthy young boy. A few days later, the boy became sick and recovered soon and never got either cowpox or smallpox.