ABSTRACT
Vaccines came about in the late 1940s and early 1950s. They were initially designed to combat bacterial infection. It was found that proteins produced by bacteria induced an immune reaction that was directed at the live bacteria in the event of infection. In the early days it was not known how this occurred. Vaccines were subsequently developed for polio, measles, and chicken pox. These vaccines were sterilized proteins injected usually in muscle tissue. Early evidence suggested that the cells in the blood somehow responded to the vaccine and developed the immunity to the pathogens. This immunity or “memory” of these pathogens was found to last some time. As time went on, it was found that white blood cells (T cells) were responsible for such immunity.
