Polio has not always been a serious and life-threatening infection. The irony is that it is a disease that has gotten worse with improved sanitation. Prior to the 1920s, polio paralysis was relatively rare. Starting in the 1930s, however, polio started to become a major threat to the newly industrialized America. Major outbreaks that affected thousands and left whole communities paralyzed spread fear throughout this country in the 1950s. Franklin D. Roosevelt pioneered government programs to fund polio research and the development of polio vaccine.

When the world was dirtier and people were frequently exposed to foods contaminated with human feces, polio frequently infected people when they were still very young. When babies get polio, they usually do not suffer the devastating paralytic complication, but they do become permanently immune to polio for the rest of their lives. When older children and adults catch the infection, however, the chance of them being paralyzed is much higher.

As living standards improved, most children did not have the opportunity to be infected when they were young because the environment around them was much cleaner. But if they caught the infection at an older age, they were more likely to suffer the severe neurological problems caused by polio. This is clearly a disease that was made more serious due to improvements in living conditions.

Consequently, as urbanization continues, the polio epidemic becomes a greater threat. During an outbreak in 1952, 3,145 people died from polio, and more than 20,000 people became permanently paralyzed from the infection. Worst of all, it is an infection that affects the poor as well as the rich and famous. Being socially privileged did not lend any protection against this scourge. There was no treatment for polio except the iron lung, which only provided supportive care during the period of the most severe paralysis.

The polio vaccine has been controversial for another reason. Prior to 2000, there were two types of polio vaccines — one containing a live but weakened virus, and another containing killed virus. The live polio vaccine is no longer given today because the vaccine could actually cause paralysis in rare circumstances (about 1 in 2 million doses). It was an accepted risk for vaccination because the risk was so much smaller than catching polio itself. However, by the early 1990s, polio had become so rare in the United States and other developed nations that the majority of the people suffering from polio paralysis actually got polio from the live polio vaccine. By that time, it did not make sense to continue using the live polio vaccine. Only the killed polio vaccine is available in the United States today.