How has medicine changed over the years? why do you only vaccinate against certain things? why not vaccinate against everything?

Limioted by vaccines: Making vaccines depend on multiple factors like the ability to isolate part of the bacteria or virus that can be given to a person without causing harm but that will generate an immune response sufficient to protect against disease. This is difficult & has been done with many infectious diseases not all. Of course many diseases are not infections (cancer, diabetes etc) so vaccination not possible.

Routine vaccinations: Vaccines have had huge public health benefits. Smallpox and polio almost completely eliminated, and measles, mumps, rubella, diptheria, chicken pox, hep b, and hpv (among others) no longer the bane of childhood. Influenza vaccine lessens flu epidemics, and Rabies Vaccine prevents death after the bite. We have vaccines for the most common and deadly infections, but not for all.

See below.: #1 medicine is much more evidence based and more expensive than before! #2 vaccines help protect against disease by helping your body develop antibodies to invading organisms . We vaccinate agains diseases where antibodies are important in preventing infection #3 many diseases are not prevented by antibodies.