Answer
Semmelweis's observations about the spread of disease in hospitals were not widely accepted until Pasteur's confirmation of the germ theory. Pasteur's work showed that microorganisms were responsible for disease, and this led to a greater understanding of the importance of sanitation and hygiene in hospitals. Semmelweis's work had shown that handwashing could prevent the spread of disease, but his ideas were not accepted until the germ theory was proven.