Polio
Polio, also known as poliomyelitis, primarily affects the gray matter of the brain and spinal cord, leading to muscle weakness and paralysis, although not all infections result in these severe outcomes. Historically referred to as "infantile paralysis," it was once thought to predominantly affect children, but it is now known that individuals of any age can contract the virus. The disease has been documented since ancient times, with significant modern understanding emerging in the 19th and 20th centuries, including the identification of three main virus strains in 1902.
The 1950s marked a critical period in the fight against polio, as widespread epidemics prompted urgent medical research. Vaccines developed by Jonas Salk and Albert Sabin led to a dramatic decline in cases after their introduction in the mid-1950s. The Salk vaccine used killed viruses, while Sabin's oral vaccine utilized live attenuated viruses. By the late 20th century, polio was virtually eradicated in the Western Hemisphere, but unvaccinated populations remained vulnerable, highlighted by outbreaks among the Amish community in the late 1970s.
Although polio remains rare in many parts of the world, isolated cases have occurred in recent years in the United States, often linked to imported infections or vaccine-derived strains. Efforts continue to enhance vaccination coverage to prevent resurgence, as public health officials emphasize the importance of immunization against this potentially debilitating disease.
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Polio
Viral disease that produced hysteria and fear among North Americans fearing its transmission during the 1950s
Before the 1950s, hundreds of thousands of North Americans were paralyzed or killed by polio, whose onset appeared to be an ordinary summer flu. The occurrence of the disease terrified millions of people and kept social activities that could lead to exposure at a minimum. Development of the polio vaccines during the decade nearly eradicated the disease and increased public confidence in biomedical science.
Polio attacks brain and spinal cord gray matter. Called “infantile paralysis” until the early 1950s, it was thought to be a disease of children that always resulted in paralysis. It was soon understood, however, that people of any age could catch polio and that victims were not always paralyzed. Historians suggest polio has afflicted humans since ancient times, because of biblical depictions of people with withered limbs. In modern times, polio was first described in 1840 by the German physician Jacob von Heine. In 1902, Karl Landsteiner discovered three polio virus strains: Brunhilde, Lansing, and Leon.
Vaccines
At the beginning of the 1950s, continuation of worldwide polio epidemics that began during the 1940s became a medical crisis in the United States. In 1950, for example, 3,400 severe cases occurred. In 1951, even more cases developed, and by 1952, there were 58,000 cases. That year, polio epidemics occurred in Europe, China, India, Japan, Korea, and the Philippines.
For Americans, the aftermath of polio was painfully clear in photos of President Franklin D. Roosevelt , who contracted the disease in 1921 and had to wear heavy steel braces on his legs. Walking was so difficult for him that he spent most of his time in a wheelchair. During the late 1940s and early 1950s, as the polio epidemic was at its worst, posters advertising the March of Dimes contained heartbreaking pictures of children on crutches and in iron lungs—the cumbersome mechanical aids that enabled polio victims with paralyzed rib cages to breathe. Before a polio vaccine became available, many parents throughout the United States and Canada panicked, keeping their children away from schools and other public facilities, such as movie theaters and swimming pools.
To counter this epidemiological crisis, the National Foundation for Infantile Paralysis funded research that led to development of vaccines by Jonas E. Salk and Albert B. Sabin during the decade. A major problem that had slowed vaccine development—the inability of polio viruses to grow outside live cells—was obviated by 1949, when Harvard researchers John Enders, Frederick C. Robbins, and Thomas H. Weller developed means to grow the polio virus outside the body. Using their technique, Salk, a University of Pittsburgh physician, developed an injected vaccine made from killed polio viruses of all three strains.
After 1954, field trials on approximately two million American children—a scope unprecedented in US medical history—began. The results were immediate, and the vaccine was pronounced safe and effective for widespread use. In 1955, mass inoculation began around the United States and the world. At the end of the 1950s, a live and oral form of the vaccine was developed by Sabin to counter problems with the Salk vaccine. The Salk and Sabin vaccines (the latter was not used until the 1960s) protected against all polio virus types. The number of polio cases declined dramatically after vaccines began being used.
Impact
The 1950s saw near eradication of this catastrophic disease that had killed or disabled millions of people worldwide. Salk’s killed vaccine and Sabin’s live vaccine are deemed by many historians to be among the most important medical discoveries of the twentieth century. Polio still occurred by the end of the 1950s, although rarely, but people no longer feared the summer months, when polio infections had been most numerous. Also, development of the tissue culture methods of Enders, Robbins, and Weller opened the door for later use of mammalian tissue cultures for advances in molecular biology that identified viral causes of cancer and acquired immunodeficiency syndrome (AIDS).
Subsequent Events
Sabin’s oral vaccine, licensed in 1961, quickly replaced Salk’s injected vaccine as the standard US polio immunizing agent because of easy administration and the belief that its live viruses would work longer than Salk’s killed viruses. Despite the effectiveness of the vaccine, polio vulnerability of unimmunized people was shown to be quite high throughout the world after the 1950s. In 1979, this was made painfully obvious by epidemics among unvaccinated Amish Americans. Retrospective studies by the World Health Organization, published in 1994, showed that once the vaccines were widely used, the Western Hemisphere quickly became free of naturally occurring polio.
Continued and minor paralytic polio outbreaks after the late 1950s occurred in situations where virus attenuation was incomplete; these outbreaks caused rethinking of the vaccine use. Reliance on the Sabin vaccine decreased in stages as time went by. In 1997, to reduce vaccine-related polio, the US Centers for Disease Control and Prevention (CDC) recommended that all children get two doses of injected (killed) vaccine, followed by two oral doses of attenuated vaccine. In 2000, to eliminate risks of vaccine-related polio, the CDC revised its recommendation to four injections of killed virus, known as an inactivated poliovirus vaccine (IPV), by age four.
A new case of polio in the United States was reported in 2013. In this instance, an infant had recently traveled into the United States from India. It was hypothesized that the infant had likely received a live, weakened portion of the virus in the form of an oral polio vaccine (OPV) while in India. Therefore, this was considered a case of poliovirus importation. In a poliovirus case reported in a US adult in 2022, scientists believed that a person who had received an OPV had likely transmitted the virus, thought to have originated outside of the United States, to the individual in New York who became infected. This was the first polio case detected in the United States since 2013. At the same time, it was reported that wastewater samples analyzed in New York City indicated a presence of the poliovirus, prompting officials to urge greater vaccination in the city.
Bibliography
Daniel, Thomas M., and Frederick C. Robbins, eds. Polio. Rochester, N.Y.: University of Rochester Press, 1997.
Gould, Tony. A Summer Plague: Polio and Its Survivors. New Haven, Conn.: Yale University Press, 1995.
Meko, Hurubie. "First Polio Case in Nearly a Decade Is Detected in New York State." The New York Times, 21 July 2022, www.nytimes.com/2022/07/21/nyregion/polio-case-new-york.html. Accessed 9 Sept. 2022.
Sherrow, Victoria. Jonas Salk. New York: Facts On File, 1993.
"Vaccine-Derived Poliovirus." Centers for Disease Control and Prevention, 3 Aug. 2022, www.cdc.gov/vaccines/vpd/polio/hcp/vaccine-derived-poliovirus-faq.html. Accessed 9 Sept. 2022.