When outbreaks of poliomyelitis plagued the United States and Europe in the late 1800s and early 1900s, the public rallied to help find a cure and poured money into research. What they got were two vaccines from the researchers Jonas Salk and Albert Sabin that largely eradicated the disease over the next 50 years.

At the turn of the 20th century, polio struck as many as 50,000 people—mainly children—in a single year. The virus paralyzed breathing muscles and could be fatal, and it left most victims permanently crippled. A vaccine was tested in 1935, but it killed six of the children in the study; it wasn’t until 1950 that the medical community felt ready to give vaccination another try.

Jonas Salk (1914–1995), a researcher at the University of Pittsburgh, proposed an injectable vaccine made from a killed virus, and a double-blind trial of nearly 2 million children was arranged. In 1955, the inactivated polio vaccine was declared safe, and Salk was hailed as a national hero. The vaccine was speedily licensed and mass produced, and more than 450 million shots were given over the next 4 years. As a result, the incidence of paralytic polio in the United States fell from 18 cases per 100,000 to fewer than 2 per 100,000.

Another vaccine containing live, weakened virus was approved in 1961 after extensive testing on children in the Soviet Union, the Netherlands, Mexico, and other countries. The new formula, developed by the University of Cincinnati researcher Albert Sabin (1906–1993), had a very small risk of actually causing polio, but it also promised extended immunity and could be taken orally, in liquid drops or sugar cubes that dissolved on the tongue. The oral polio vaccine largely replaced Salk’s version as the predominant vaccine used in the United States and most other countries. By the 1970s, the annual incidence of polio in the United States had declined a thousandfold from prevaccine levels, to an average of 12 cases a year.

ADDITIONAL FACTS

  1. Both types of polio vaccines generally require three doses, with a fourth “booster” given when a child reaches school age.
  2. The World Health Organization in 1988 called for the global eradication of polio by the year 2000. Complete elimination by the target date didn’t happen, but the number of new cases each year had been reduced to approximately 1,000 to 2,000 (down from more than 250,000).
  3. In November 2005, four Amish children in Minnesota were diagnosed with polio. None of them had been vaccinated.