April 12, 1955: The polio vaccine is declared safe and effective.
After its clinical identification in the late 18th century, poliomyelitis remained one of the public’s most feared diseases in most industrialized nations until the initiation of a wide-scale effort to vaccinate against the disease in the mid-1900s. In 1894, the first known epidemic of polio to break out in the United States struck a population in Vermont. Over the next few decades, outbreaks of polio reached pandemic proportions in much of the West. Then often referred to ominously as “infantile paralysis”, the spread of polio in industrialized nations was accelerated by the loss of natural immunities to the disease as a result of improved sanitation and sewage disposal. As noted in the report from the original 1894 Vermont outbreak, a dreaded and relatively common outcome of the disease was paralysis of some or all of the extremities. The sinister image of the iron lung, upon which an affected child might become dependent as a result of paralysis of muscles in the chest, was embedded in the public’s conception of the disease. Amid dreams of idyllic American suburban life and the ultimate triumph of modern science over nature, polio, writes David Oshinsky, was “the crack in the fantasy”.
Efforts toward a vaccine gained traction in the late 1930s. In 1952, the worst outbreak of polio in the nation’s history affected some 58,000 people. Of these, 3,145 died, and 21,000 were left with some degree of paralysis. The same year, Jonas Salk and colleagues developed and tested a polio vaccine on schoolchildren. In 1954, one of the largest and most publicized clinical trials in the nation’s history was underway. The trials involved the injection of the vaccine and placebos in 623,972 American schoolchildren and resulted in an 80-90% success rate in preventing paralytic polio. On April 12, 1955, the results of these trials were announced and the vaccine was declared to be “safe, effective, and potent”. With the development of this viable vaccine, widespread mass vaccination campaigns took place and, for the most part, reduced the impact - and public fear - of polio nationally. Since 1988, worldwide polio cases have decreased by pver 99%; however, the disease still persists in several countries.