1718 - Lady Mary Wortley Montagu, the wife of the British ambassador to Constantinople, observed the positive effects of variolation on the native population and had the technique performed on her own children.
1878 - Confirmation and popularization of the germ theory of disease (Louis Pasteur)
1880 - 1881 -Theory that bacterial virulence could be attenuated by culture in vitro and used as vaccines. Proposed that live attenuated microbes produced immunity by depleting host of vital trace nutrients. Used to make chicken cholera and anthrax "vaccines" (Louis Pasteur)
1883 - 1905 - Cellular theory of immunity via phagocytosis by macrophages and microphages (polymorhonuclear leukocytes) (Elie Metchnikoff)
1885 - Introduction of concept of a "therapeutic vaccination". First report of a live "attenuated" vaccine for rabies (Louis Pasteur).
1890 - Demonstration of antibody activity against diphtheria and tetanus toxins. Beginning of humoral theory of immunity. (Emil von Behring) and (Shibasaburo Kitasato)
1891 - Demonstration of cutaneous (delayed type) hypersensitivity (Robert Koch)
1893 - Use of live bacteria and bacterial lysates to treat tumors-"Coley's Toxins" (William B. Coley)
1949 - growth of polio virus in tissue culture, neutralization with immune sera, and demonstration of attenuation of neurovirulence with repetitive passage (John Enders) and (Thomas Weller) and (Frederick Robbins)