Mandates to Vaccinate: A Brief HistoryA scabby, itchy pustule that left behind a permanent scar on the outside of the upper arm—as the main side effect of the smallpox vaccine, this scar was often used as a “vaccination passport,” proving inoculation for millions of Americans in the wake of vaccination mandates at the turn of the 20th century, when the highly contagious smallpox disease pummeled through communities. By 1980, the World Health Organization declared that this often-deadly virus which had been circulating the world for over 3,000 years had been eradicated.