Polio

Probably no disease created as much fear as polio. Paralysis and death were the major hazards of- this disease. Probably the most famous polio victim in the United States, perhaps even in the world, was President Franklin D. Roosevelt, who hid the extent of his disability from the public throughout his presidency. Polio was one of the most dreaded childhood diseases of the 20th century. The first clinical description of polio dates to 1789 when a British physician provided the first description of the disease (debility of the lower extremities). The first known large epidemic occurred in 1916, killing 6,000 people and leaving 27,000 more paralyzed.[17] In retrospect, isolation and quarantine were not effective means of controlling the disease. A race to develop an effective polio vaccine began in the 1930s, and unfortunately early clinical trials failed in that many individuals ended up infected with polio, which clearly was not the intent of the vaccine developers.

Widespread epidemics of polio were documented after World War II, with an average of more than 20,000 cases a year occurring between 1945 and 1949. In 1952, there were 58,101 cases of polio in the United States, the most ever counted. By the mid-20th century, "polio hysteria" fueled fear across the country.

The difficulty in developing a polio vaccine stemmed from the fact that this disease is caused by three strains of virus. Understanding the polioviruses took decades, with much of the research funded by the March of Dimes Foundation, a grassroots organization founded with the help of President Roosevelt.

In the late 1940s, Dr. Jonas Salk began to use the newly developed tissue cultures method of cultivating and working with the poliovirus. The first safe and effective vaccine, the Salk-injected vaccine, used killed poliovirus. During the 1950s, massive trials of the Salk vaccine, unprecedented in medical history, were conducted and led to a nationwide mass immunization campaign promoted by the March of Dimes. This effort led to a significant drop in the number of new cases of polio in the United States, and in 1955, the inactivated polio vaccine was licensed for use in the United States.

While the vaccine helped stop polio in its tracks, there were problems with the vaccine related to the incomplete inactivation of some virus particles. This was soon corrected.

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During this time, Dr. Albert Sabin, a bitter rival of Salk, also was working on a polio vaccine. His vaccine used live, attenuated (weakened) virus rather than killed poliovirus. Whereas the Salk vaccine required injections, the Sabin vaccine was oral. Field trials of this vaccine proved the Sabin oral vaccine to be effective; the oral, live-virus polio vaccine was licensed in 1961. Because live vaccine contains a weakened type of poliovirus that could in theory mutate into more virulent forms (albeit exceedingly rare, but not unheard of), it is not given to people with impaired immune systems. The oral vaccine was superior in terms of ease of administration, and it also provided long-lasting immunity. Both vaccines have advantages and disadvantages with regard to safety and cost, and both are used throughout the world.