1847 Ignaz Semmelweiss (Vienna) discovers transmission and prevention of puerperal fever (mostly strep infections immediate post partum) and the need to wash hands. He faced ostracism and refection and ridicule http://www.mja.com.au/public/issues/177_11_021202/dec10354_fm.html Later in life beaten down from the controversy, he died from a strep infection himself.
Regarding John Snow - father of epidemiology and public health, from Lancet (one of the most prestigious medical journals even today) on June 23, 1855 It is the misfortune of medicine....treasonable behavior by one of its own.
Lister and antisepsis (30 years)
Papanicolaou and the pap smear and modern cytology (25 years) see Dr. George Papanicolaou, a dedicated researcher
Goldberger and Pellagra
Community Driven Approach