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Vaccine Safety > Issues of Interest > AIDS
Oral Polio Vaccine and HIV / AIDS:
Questions and Answers
Human Immunodeficiency Virus (HIV)
Acquired Immunodeficiency Syndrome (AIDS)

Q&A image

In the early 1990s an article in Rolling Stone magazine introduced the idea that an experimental oral polio vaccine used in the late 1950s may have caused the AIDS epidemic. In 1999 the idea was presented again in Mr. Edward Hooper’s book ‘The River’. In response to these publications, research has been done to test the validity of the oral polio vaccine/HIV theory. Evidence about the genetic origin and characteristics of HIV, the production of the experimental oral polio vaccine, and the lack of HIV/AIDS epidemics in some areas where the experimental oral polio vaccine was given all suggest that the experimental vaccine was not the source of HIV and AIDS in people. Furthermore, some of the remaining experimental vaccine was recently tested and did not contain HIV or HIV-like viruses. In conclusion, scientists believe that the experimental oral polio vaccine did not cause the HIV/AIDS epidemic.

Current oral polio vaccines are not related to the experimental vaccine used in Africa in the 1950s. Modern vaccines are always tested before use and DO NOT contain HIV. Immunization is one of the most effective health interventions in the world. Parents should continue to have their children vaccinated against polio and other childhood diseases. There is no reason to fear that children will be infected by HIV through polio vaccination.

  1. What is polio?

    Poliomyelitis, or Polio, is caused by a virus that lives in the throat and intestinal tract. It is spread through contact with the bowel movements of an infected person (for example, by changing diapers). Polio can cause cold-like symptoms, pain and stiffness in the neck, back, and legs, and, in the worst cases, paralysis or death. Polio was one of the most dreaded childhood diseases of the first half of the 20th Century in the United States. Polio vaccine became available in 1955 and because of vaccination the disease has disappeared from the U.S., and efforts are underway to eliminate polio from the rest of the world as well. It would only take one case of polio from another country to bring the disease back if we were not protected through vaccination.
  1. What is polio vaccine and is it safe?

    Polio vaccine protects people against polio. There are two types of polio vaccine: Inactivated polio vaccine, called IPV, which is given as a shot (the polio virus used in this vaccine is killed); and live oral polio vaccine, called OPV, which is a liquid that is swallowed (the virus used in this vaccine is attenuated or weakened). Currently in the U.S. we use only IPV, but in parts of the world where polio still exists people get vaccinated with OPV. Both OPV and IPV protect against polio, but OPV is better at keeping the disease from spreading to other people. However, in rare cases (about 1 in 2.4 million), OPV actually causes polio. Since the risk of getting polio in the U.S. is now rare, experts believe that the benefits of OPV no longer outweigh the slight risks. IPV does not cause polio or any other serious problems. Some people who get IPV get a sore spot where the shot was given, but most don’t have any problems at all with it.


  1. How is polio vaccine made?

    IPV is made with dead polio virus. The virus is grown in a lab on a type of monkey kidney cell culture and then killed with formaldehyde or other chemical(s) harmful to the virus. The chemicals are removed before the dead virus is added to the vaccine. OPV is made with live polio virus that has been weakened so that it does not have enough strength left to cause disease. Polio virus that is used to make OPV is also grown in a lab on monkey kidney cell culture and then weakened using chemicals, freezing and dilution before being given to people as a vaccine..
  1. When were polio vaccines first developed and tested?

    The first polio vaccines were developed and tested in the 1950s. Jonas Salk introduced the first widely used vaccine in 1954, which was given to people as a shot (IPV). A short time later Salk’s shot was replaced by an oral polio vaccine (OPV) developed by Albert Sabin. This vaccine was placed on a sugarcube and eaten. In 1957 another scientist, Dr. Hilary Koprowski, began vaccinating people with an experimental oral polio vaccine (OPV) that was dropped into the recipient’s mouth and swallowed.


  1. Were animals used in developing and testing polio vaccines?

    Testing on animals, especially animals that are closely related to humans such as monkeys and chimpanzees, gave researchers a good idea about the safety and efficacy of their vaccine before giving the vaccine to people. Early polio vaccine tests were done with rabbits, mice, guinea pigs, chimpanzees and monkeys. Also, animal organs were used to grow the polio virus that was killed or weakened to make the vaccines. Monkeys were the most common animal used to grow the polio virus for early vaccines.
  1. Is it true that HIV originally came from monkeys and apes?

    There are two types of HIV (human immunodeficiency virus) that can cause AIDS, HIV-1 and HIV-2. HIV-1 causes most cases of AIDS in the U.S., only a few cases of HIV-2 have been found in the U.S. HIV-2 is mostly an infection of persons from West Africa. Scientists think that HIV-1 evolved from an immunodeficiency virus found in chimpanzees (simian immunodeficiency virus, or SIVcpz). Viruses that infect one species of animal, such as chimpanzees, generally don’t infect other species of animals, such as humans. Therefore, scientists do not know exactly how or why this particular virus ‘jumped’ from chimpanzees to people—also known as ‘cross-species transmission’. Scientists do believe, however, that SIVcpz evolved into HIV-1 many decades ago. DNA and genetic test results of HIV-1 indicate that it may have crossed into humans in the 1930s (Korber et al. 2000, Hahn et al. 2000). HIV-2 is believed to have come from a cross-species transmission of an SIV from a sooty mangabey monkey (SIVsm) (Hahn et al. 2000).


  1. What theory on polio vaccine and the origin of AIDS is described by Mr Edward Hooper in The River?

    Mr. Hooper describes a theory that HIV was introduced by an experimental oral polio vaccine used in Central Africa in the 1950s. The vaccine (from the CHAT strain) was produced by Dr. Hilary Koprowski and his colleagues at the Wistar Institute.
  1. Is Dr. Koprowski’s vaccine related to the polio vaccines now being used worldwide?

    No, the current oral polio vaccine was developed by Dr. Albert Sabin, uses Sabin strains and bears no relationship to the experimental vaccine. Furthermore, modern polio vaccines are demonstrated to be free of HIV.


  1. Is there any evidence that supports the theory that HIV was introduced by an experimental oral polio vaccine?

    The theory relies almost exclusively on the coincidental appearance of the earliest documented cases of AIDS near some of the sites where the vaccine was tested in Central Africa.
  1. Where was the vaccine used and how many people were vaccinated?

    The vaccine of Dr Koprowski was given to 7.2 million people in Poland, 1.5 million in Croatia, 215,000 in Burundi, 76,000 in the former Belgian Congo (now the Democratic Republic of the Congo) and 34,000 in Switzerland. The vaccine tested in Poland and Kinshasa (DR Congo) was from the same vaccine lot.


  1. Did early cases of HIV appear wherever the Koprowski vaccine was tested?

    No. The vaccine was tested in several places in Europe and Africa, including Poland, Switzerland, Croatia, Burundi and Kinshasa (DR Congo). Early cases of AIDS were seen only in Central Africa. If the vaccine had been contaminated with HIV or a similar virus, it is likely that at least some of the people who were vaccinated in the European countries would have contracted the virus as well.
  1. What is the explanation for the fact that some of the areas where the Koprowski oral polio vaccine was given were close to the areas where the first AIDS outbreaks were seen?

    The areas where Koprowski’s vaccine was used and where the first AIDS outbreaks occurred are also areas where chimpanzees that carry SIV live. So it makes sense that those areas were the same areas where SIV ‘jumped’ from chimpanzees to people, and HIV-1 and AIDS were first seen. Though some people believe that Dr. Koprowski did use chimpanzee organs to grow the virus for the vaccine, evidence indicates that chimpanzees were only used to test the vaccine, not to produce it.


  1. If so many people in various places received the Koprowski vaccine, how does Mr Hooper explain that there were not a large number of AIDS cases appearing simultaneously?

    Mr. Hooper suggests that the suspect vaccine only had low level contamination or that only certain lots of vaccine were contaminated.
  1. Is there any documentation that early AIDS cases actually received the vaccine?

    No, there are no records to show that the AIDS cases did in fact receive the vaccine.


  1. How does Mr. Hooper suggest the vaccine could have become contaminated?

    Mr. Hooper suggests that all of the following events might have occurred: (1) chimpanzee tissues contaminated with an HIV-like virus were used in the production of the experimental vaccine lots, (2) an HIV-like virus grew during vaccine production and (3) HIV could be transmitted during oral vaccination.
  1. Was chimpanzee tissue used to produce the vaccine?

    No, the vaccine was produced in cells from Asian monkeys, of India or the Philippines, which do not carry HIV-like viruses. Mr. Hooper’s book relies on the assumption that some vaccine was produced using chimpanzee tissues outside of standard protocols.
  2. Will HIV or HIV-like viruses grow in cell cultures like those used to produce the vaccine?

    No, HIV and related viruses do not grow in cultures of kidney cells like those used to produce the vaccine.


  1. If an oral polio vaccine were contaminated with an HIV-like virus, would that result in infection of vaccine recipients?

    It is very difficult to transmit HIV by the oral route. It is highly unlikely that HIV infection would result from a vaccine given by mouth.
  1. If chimpanzees are the source of HIV, are there other ways that humans could have become infected from them?

    There is evidence that chimpanzees may be the original source of HIV. It has been clear since the earliest years of the AIDS epidemic that HIV is most efficiently spread by blood and sexual fluids. Chimpanzees are hunted for food in Central Africa. Exposure to chimpanzee blood during hunting and preparing the carcass for food could result in infection through skin cuts or other lesions. Hunters could have spread HIV-like virus to others through sexual contact. It has been suggested that urbanization, the breakdown of traditional family life, new attitudes about sexuality and improved transportation all facilitated the spread of AIDS.
  2. Was the experimental vaccine tested for HIV?

    The vaccine was not tested for HIV in the 1950s because no one knew about the virus then. Tests for HIV and related viruses did not become available until the 1980s. However, some of Dr. Koprowski’s vaccine that had been stored in a lab was recently tested and did not contain any HIV or HIV-like viruses. Furthermore, the vaccine tests did not show any evidence of chimpanzee cells, which suggests that chimpanzee organs were not used to grow the virus for the vaccine and the vaccine, therefore, was not contaminated with SIV, the HIV-like virus. (Cohen 2000, Cohen 2001, Horton 2000, Rizzo et al. 2001, Weiss 2001).
  1. Can testing of the vials of material used to make the Koprowski vaccine prove that the theory is not correct?

    No. Mr Hooper and others have stated that a negative test could be due to the vials coming from the wrong lots, having been improperly stored or the test being insufficiently sensitive to detect the postulated extremely low level of contamination.
  1. Have polio vaccines ever been contaminated with other viruses?

    Yes. Some of the first Salk polio vaccines and Sabin polio vaccines were contaminated with SV-40, a virus found in some species of monkey. SV-40 is not related to HIV. Studies have shown no increased rates of disease among persons who received that vaccine. Modern vaccines do not contain SV-40. The Sabin vaccine seed strains, which are used to make modern OPV, have been repeatedly tested using very sensitive assays and shown to be free of any virus contamination.
  2. Is it possible to get HIV from vaccines that are used today?

    No--All vaccines used today have to go through testing and evaluation before and after they are licensed for use. This begins with extensive testing in labs and animals, followed by three phases of testing on groups of human volunteers. In addition, tissues and cells used to grow and produce any biological item, such as vaccines, are required to be tested and cleared of any viruses, including HIV (FDA 1993). If a vaccine passes all of these rigorous scientific tests it may be approved by the Food and Drug Administration (FDA) and licensed for use. The FDA and CDC continue to monitor a vaccine, even after it is tested and licensed, to make sure that it continues to be safe (for more information, see

    The Vaccine Adverse Event Reporting System, or VAERS, was designed to give health care workers and others a place to report negative reactions following vaccination. VAERS helps the FDA and CDC to continuously monitor vaccine safety. To request a VAERS form or to get more information about VAERS please go to or call 1-800-822-7967.



Cohen J. Disputed AIDS theory dies its final death. Science 2001;292:615.

Cohen J. Vaccine theory of AIDS origins disputed at Royal Society. Science 2000;289:1850-1851.

FDA. Points to consider in the characterization of cell lines used to produce biologicals. 1993

Hahn B, Shaw G, De Cock K, Sharp P. AIDS as a zoonosis: scientific and public health implications. Science 2000;287:607-614.

Horton R. New data challenge OPV theory of AIDS origin. Lancet 2000;356:1005.

Korber B, Muldoon M, Theiler J, Gao F, Gupta R, Lapedes A, Hahn BH, Wolinsky S, Bhattacharya T. Timing the ancestor of the HIV-1 pandemic strains. Science 2000;288:1789-1796.

Rizzo P, Matker C, Powers A, Setlak P, Heeney JL, Ratner H, Carbone M. No evidence of HIV and SIV sequences in two separate lots of polio vaccines used in the first U.S. polio vaccine campaign. Virology 2001;287:13-17.

Weiss R. Polio vaccines exonerated. Nature 2001;410:1035-1036.

See also: FACT SHEET on Polio Vaccine and HIV/AIDS

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This page last modified on March 23, 2004


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