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The Man Who Made Polio History

Few people who were alive at the time can forget what happened in the years from 1938 to 1955. U.S. President Franklin D. Roosevelt—himself a polio survivor—rallied his country to a war on polio. With the creation of the National Foundation for Infantile Paralysis (now the March of Dimes) in 1938, a massive fundraising effort began to support care for polio patients and research by top scientists on virology, immunology, and epidemiology. The cause became more urgent in the years after World War II, as polio epidemics worsened: At their peak in 1952, the United States reported some 58,000 polio cases.

Then, on April 12, 1955-10 years to the day after Roosevelt's death-the March of Dimes announced that the Salk vaccine was both safe and effective.

Success quickly followed: In 1957, the first year the vaccine was widely available, the number of U.S. polio cases dropped to 5,000. By 1960, annual polio cases were down to 3,000. The last case of wild polio in the United States was recorded in 1979; in Latin America, in 1991. By 1994-after a generation of polio immunizations-the Americas as a region was declared polio-free.

Doctors and parents around the world this year are paying tribute to Jonas Salk and his polio vaccine. But how much credit really belongs to Salk?

The great race

Some argue that John Enders of Harvard University deserves much of the glory, and in fact he and colleagues Thomas Weller and Frederick Robbins eventually won the Nobel Prize for their research associated with polio. Their groundbreaking work made it possible to grow poliovirus in laboratory cell cultures, setting the stage for subsequent polio vaccine development.

The work of Julius Youngner, a member of Salk's team at the University of Pittsburgh, also was crucial. Youngner developed a method known as trypsinization that allowed poliovirus to be grown in tissue from monkey kidneys rather than in the human fetal cells used by Enders. This set the stage for large-scale production of virus and vaccine.

Salk himself entered the polio picture as a virologist at the University of Pittsburgh Medical School, where he originally specialized in influenza. Salk's initial involvement was in typing the poliovirus, as a way to earn money to expand his lab.

Bankrolled and encouraged by the March of Dimes, Salk progressed rapidly in his research toward a killed-virus vaccine, and by the summer of 1954, he was ready to test an experimental version nationwide. Over the objections of critics including Enders and vaccine rival Albert Sabin, Salk and the March of Dimes launched what was then the largest field trial ever attempted. Its subjects were the "Polio Pioneers," nearly 2 million children (including Salk's own three sons) whose parents volunteered them to participate in the trials. Salk's mentor, the eminent University of Michigan epidemiologist Thomas Francis, Jr., oversaw the effort, earning his own honored place in polio history. It was Francis who announced on April 12, 1955, "The vaccine works. It is safe, effective and potent."

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