page_title: Polio vaccine
section_title: Contamination concerns
hierarchical_section_title: Polio vaccine / Side effects / Contamination concerns
caption_attribution_description: For documentary purposes the German Federal Archive often retained the original image captions, which may be erroneous, biased, obsolete or politically extreme. Polio-Schutzimpfung im Gesundheitsamt Bonn
context_page_description: Polio vaccines are vaccines used to prevent poliomyelitis. Two types are used: an inactivated poliovirus given by injection and a weakened poliovirus given by mouth. The World Health Organization recommends all children be fully vaccinated against polio. The two vaccines have eliminated polio from most of the world, and reduced the number of cases reported each year from an estimated 350,000 in 1988 to 33 in 2018.
  The inactivated polio vaccines are very safe. Mild redness or pain may occur at the site of injection. Oral polio vaccines cause about three cases of vaccine-associated paralytic poliomyelitis per million doses given. This compares with 5,000 cases per million who are paralysed following a polio infection. Both are generally safe to give during pregnancy and in those who have HIV/AIDS but are otherwise well.
  The first successful demonstration of a polio vaccine was by Hilary Koprowski in 1950, with a live attenuated virus which people drank. The vaccine was not approved for use in the United States, but was used successfully elsewhere. An inactivated polio vaccine, developed a few years later by Jonas Salk, came into use in 1955.
context_section_description: In 1960, the rhesus monkey kidney cells used to prepare the poliovirus vaccines were determined to be infected with the simian virus-40 (SV40), which was also discovered in 1960 and is a naturally occurring virus that infects monkeys. In 1961, SV40 was found to cause tumors in rodents. More recently, the virus was found in certain forms of cancer in humans, for instance brain and bone tumors, pleural and peritoneal mesothelioma, and some types of non-Hodgkin lymphoma. However, SV40 has not been determined to cause these cancers.
  SV40 was found to be present in stocks of the injected form of the IPV in use between 1955 and 1963. It is not found in the OPV form. Over 98 million Americans received one or more doses of polio vaccine between 1955 and 1963 when a proportion of vaccine was contaminated with SV40; an estimated 10–30 million Americans may have received a dose of vaccine contaminated with SV40. Later analysis suggested that vaccines produced by the former Soviet bloc countries until 1980, and used in the USSR, China, Japan, and several African countries, may have been contaminated, meaning hundreds of millions more may have been exposed to SV40.
  In 1998, the National Cancer Institute undertook a large study, using cancer case information from the institute's SEER database. The published findings from the study revealed no increased incidence of cancer in persons who may have received vaccine containing SV40. Another large study in Sweden examined cancer rates of 700,000 individuals who had received potentially contaminated polio vaccine as late as 1957; the study again revealed no increased cancer incidence between persons who received polio vaccines containing SV40 and those who did not. The question of whether SV40 causes cancer in humans remains controversial, however, and the development of improved assays for detection of SV40 in human tissues will be needed to resolve the controversy.
  During the race to develop an oral polio vaccine, several large-scale human trials were undertaken. By 1958, the National Institutes of Health had determined that OPV produced using the Sabin strains were the safest. Between 1957 and 1960, however, Hilary Koprowski continued to administer his vaccine around the world. In Africa, the vaccines were administered to roughly one million people in the Belgian territories (now the Democratic Republic of the Congo, Rwanda, and Burundi). The results of these human trials have been controversial, and unfounded accusations in the 1990s arose that the vaccine had created the conditions necessary for transmission of simian immunodeficiency virus from chimpanzees to humans, causing HIV/AIDS. These hypotheses, however, have been conclusively refuted. By 2004, cases of poliomyelitis in Africa had been reduced to just a small number of isolated regions in the western portion of the continent, with sporadic cases elsewhere. Recent local opposition to vaccination campaigns have evolved due to lack of adequate information, often relating to fears that the vaccine might induce sterility. The disease has since resurged in Nigeria and in several other African nations without necessary information, which epidemiologists believe is due to refusals by certain local populations to allow their children to receive the polio vaccine.
caption: Doses of oral polio vaccine are added to sugar cubes for use in a 1967 vaccination campaign in Bonn, West Germany
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