Radioactivity not only helps us combat disease, it also enables us to study how drugs work in the body. Then there is Pasteur who found that bacteria cause disease and infection. The ability to transplant organs in a way that will be retained by the body is another real milestone. The serendipitous discovery of penicillin launched the search for antibiotics in all kinds of organisms. And the discovery of the genetic code opened a window onto research into hereditary characteristics and diseases.
Vaccines are yet another breakthrough.
Later, Pasteur developed a vaccine against rabies, which consisted of a weakened form of the rabies virus. I do not have a crystal ball, but I think immunological approaches to the treatment of cancer are really beginning to take off. This means scientists are working on all sorts of manipulations to teach the body to recognize cancer cells as foreign, so our bodies will reject them. In addition, there is a tremendous amount of work now under way on the chemotherapy of viruses. The ebola virus is an example.