In the early 1880s, Wallace was drawn into the debate over mandatory smallpox vaccination. Wallace originally saw the issue as a matter of personal liberty; but, after studying some of the statistics provided by anti-vaccination activists, he began to question the efficacy of vaccination. At the time, the germ theory of disease was very new and far from universally accepted. Moreover, no one knew enough about the human immune system to understand why vaccination worked. When Wallace did some research, he discovered instances where supporters of vaccination had used questionable, in a few cases completely phony, statistics to support their arguments. Always suspicious of authority, Wallace suspected that physicians had a vested interest in promoting vaccination, and became convinced that reductions in the incidence of smallpox that had been attributed to vaccination were, in fact, due to better hygiene and improvements in public sanitation.