In a generic sense, vaccination works by priming the
immune system with an "
immunogen". Stimulating immune response, by use of an infectious agent, is known as
immunization. The development of immunity to polio efficiently blocks person-to-person transmission of wild poliovirus, thereby protecting both individual vaccine recipients and
the wider community.
1930s In the early 1930s,
Maurice Brodie led a team from the public health laboratory of the city of New York, while
John A. Kolmer collaborated with the
Research Institute of Cutaneous Medicine in Philadelphia.
Kolmer's live vaccine Kolmer began his vaccine development project in 1932 and ultimately focused on producing an attenuated or
live virus vaccine. Inspired by the success of vaccines for rabies and yellow fever, he hoped to use a similar process to denature the polio virus. Using methods of production that were later described as "hair-raisingly amateurish, the therapeutic equivalent of bath-tub gin", Kolmer ground the spinal cords of his infected monkeys and soaked them in a salt solution. He then filtered the solution through mesh, treated it with
ricinolate, and refrigerated the product for 14 days In keeping with the norms of the time, Kolmer completed a relatively small animal trial with 42 monkeys before proceeding to
self-experimentation in 1934. He tested his vaccine upon himself, his two children, and his assistant. Kolmer's first formal presentation of results did not come about until November 1935, when he presented the results of 446 children and adults he had vaccinated with his attenuated vaccine. ultimately finding a solution of
formaldehyde to be the most effective. By 1 June 1934, Brodie was able to publish his first scholarly article describing his successful induction of immunity in three monkeys with inactivated poliovirus. Through continued study on an additional 26 monkeys, Brodie ultimately concluded that administration of live virus vaccine tended to result in
humoral immunity, while administration of killed virus vaccine tended to result in
tissue immunity. declared the vaccine safe. At this time, very little oversight of medical studies occurred and the ethical treatment of study participants largely relied upon moral pressure from
peer academic scientists. Both Kolmer and Brodie were called to present their research at the Annual Meeting of the
American Public Health Association in
Milwaukee, Wisconsin, in October 1935.
1948 A breakthrough came in 1948 when a research group headed by
John Enders at the
Children's Hospital Boston successfully cultivated the poliovirus in human tissue in the laboratory. This group had recently successfully grown
mumps in
cell culture. In March 1948,
Thomas H. Weller was attempting to grow
varicella virus in embryonic lung tissue. He had inoculated the planned number of tubes when he noticed that a few unused tubes. He retrieved a sample of
mouse brain infected with poliovirus and added it to the remaining test tubes, on the off chance that the virus might grow. The
varicella cultures failed to grow, but the polio cultures were successful. This development greatly facilitated vaccine research and ultimately allowed for the development of vaccines against polio. Enders and his colleagues,
Thomas H. Weller and
Frederick C. Robbins, were recognized in 1954 for their efforts with a
Nobel Prize in Physiology or Medicine. Other important advances that led to the development of polio vaccines included the identification of three poliovirus serotypes (poliovirus type 1 – PV1, or Mahoney; PV2, Lansing; and PV3, Leon), the finding that before paralysis, the virus must be present in the blood, and the demonstration that administration of antibodies in the form of
gamma globulin protects against paralytic polio.
1950–1955 During the early 1950s, polio rates in the U.S. were above 25,000 annually; in 1952 and 1953, the U.S. experienced an outbreak of 58,000 and 35,000 polio cases, respectively, up from a typical number of some 20,000 a year, with deaths in those years numbering 3,200 and 1,400. Amid this U.S. polio epidemic, millions of dollars were invested in finding and marketing a polio vaccine by commercial interests, including Lederle Laboratories in New York under the direction of
H. R. Cox. Also working at Lederle was Polish-born
virologist and
immunologist Hilary Koprowski of the Wistar Institute in Philadelphia, who tested the first successful polio vaccine, in 1950. On 27 February 1950, Koprowski's live, attenuated vaccine was tested for the first time on an 8-year-old boy living at
Letchworth Village, an institution for physically and mentally disabled people located in New York. After the child had no side effects, Koprowski enlarged his experiment to include 19 other children.
Jonas Salk himself, in 1957 at the
University of Pittsburgh, where his team had developed the vaccine circa 1961 for the National Polio Immunization Program The first effective polio vaccine was developed in 1952 by
Jonas Salk and a team at the
University of Pittsburgh that included
Julius Youngner, Byron Bennett, L. James Lewis, and Lorraine Friedman, which required years of subsequent testing. Salk went on CBS radio to report a successful test on a small group of adults and children on 26 March 1953; two days later, the results were published in
JAMA.
Leone N. Farrell invented a key laboratory technique that enabled the mass production of the vaccine by a team she led in Toronto. Beginning 23 February 1954, the vaccine was tested at
Arsenal Elementary School and the
Watson Home for Children in
Pittsburgh, Pennsylvania. Salk's vaccine was then used in a test called the Francis Field Trial, led by
Thomas Francis, the largest medical experiment in history at that time. The test began with about 4,000 children at Franklin Sherman Elementary School in
McLean, Virginia, and eventually involved 1.8 million children, in 44 states from
Maine to
California. By the conclusion of the study, roughly 440,000 received one or more injections of the vaccine, about 210,000 children received a
placebo, consisting of harmless
culture media, and 1.2 million children received no vaccination and served as a control group, who would then be observed to see if any contracted polio. Soon after Salk's vaccine was licensed in 1955, children's vaccination campaigns were launched. In the U.S., following a mass immunization campaign promoted by the
March of Dimes, the annual number of polio cases fell from 35,000 in 1953 to 5,600 by 1957. By 1961 only 161 cases were recorded in the United States. A week before the announcement of the Francis Field Trial results in April 1955,
Pierre Lépine at the
Pasteur Institute in Paris had also announced an effective polio vaccine.
Safety incidents In April 1955, soon after mass polio vaccination began in the US, the Surgeon General began to receive reports of patients who contracted paralytic polio about a week after being vaccinated with the Salk polio vaccine from the
Cutter pharmaceutical company, with the paralysis starting in the limb the vaccine was injected into. The Cutter vaccine had been used in vaccinating 409,000 children in the western and midwestern United States. Later investigations showed that the Cutter vaccine had caused 260 cases of polio, killing 11.
1961 (right) with
Robert Gallo, circa 1985 At the same time that Salk was testing his vaccine, both
Albert Sabin and Hilary Koprowski continued working on developing a vaccine using live virus. During a meeting in Stockholm to discuss polio vaccines in November 1955, Sabin presented results obtained on a group of 80 volunteers, while Koprowski read a paper detailing the findings of a trial enrolling 150 people. Koprowski in the Congo and Poland. Sabin's oral vaccine using live virus came into commercial use in 1961.
1987 An enhanced-
potency IPV was licensed in the United States in November 1987, and is currently the vaccine of choice there. In some countries, a fifth vaccination is given during
adolescence. containing IPV was approved for use in the United States. and the
Rotary Foundation, began in 1988, and has relied largely on the oral polio vaccine developed by
Albert Sabin and
Mikhail Chumakov (Sabin-Chumakov vaccine).
After 1990 Polio was eliminated in the Americas by 1994. The disease was officially eliminated in 36 Western Pacific countries, including China and Australia, in 2000. Europe was declared polio-free in 2002. Since January 2011, no cases of the disease have been reported in India, hence in February 2012, the country was taken off the WHO list of polio-endemic countries. In March 2014, India was declared a polio-free country. Although poliovirus transmission has been interrupted in much of the world, transmission of wild poliovirus does continue and creates an ongoing risk for the importation of wild poliovirus into previously polio-free regions. If importations of poliovirus occur, outbreaks of poliomyelitis may develop, especially in areas with low vaccination coverage and poor sanitation. As a result, high levels of vaccination coverage must be maintained. As of 2014, polio virus had spread to 10 countries, mainly in Africa, Asia, and the
Middle East, with Pakistan, Syria, and
Cameroon advising vaccinations to outbound travellers. Polio vaccination programs have been resisted by some people in Pakistan and Afghanistan – the two countries with remaining wild polio cases as of 2020. Almost all Muslim religious and political leaders have endorsed the vaccine, but a fringe minority believes that the vaccines are secretly being used for the sterilisation of Muslims. The fact that the
CIA organized a fake vaccination program in 2011 to help find
Osama bin Laden is an additional cause of distrust. In 2015, the WHO announced a deal with the
Taliban to encourage them to distribute the vaccine in areas they control. However, the Pakistani Taliban was not supportive. On 11 September 2016, two unidentified gunmen associated with the Pakistani Taliban, Jamaat-ul-Ahrar, shot Zakaullah Khan, a doctor who was administering polio vaccines in Pakistan. The leader of the Jamaat-ul-Ahrar claimed responsibility for the shooting and stated that the group would continue this type of attack. Such resistance to and skepticism of vaccinations has consequently slowed down the polio eradication process within the two remaining endemic countries. == Travel requirements ==